Fate cosplaying as Mizuki Nana? WIN!
I don’t think it’s uncommon to start watching (or continuing watching) a series because either the OP song or ED song was really good. Many times its that OP sequence that is one’s first impression of a series. More times than not, if a song is lousy, slow/dull, or lackluster, I’m already in a poor state of mind before I’ve actually seen any part of the episode. There are many OP, ED, character, and insert songs that I really enjoy, so it was pretty hard to select only a handful of them.
After some brainstorming, here is my list of 15 favorite OP/ED songs. I thought about imposing the 6 month rule–not being able to list something from a series that is less than 6 months old because of recency effects, but that would eliminate a lot of potential stuff. You’ll just have to read on to see whether or not that will actually mattered. 
I was originally going to do a top 10, but as I was going through the long list I made, I just could not drop some. The only rules I employed was that I could not select more than 1 song per artist.
15. marble – Maebe Drive (Hidamari Sketch ED)
Starting things off is one the most addicting tunes I’ve heard in a long while. There is something about calming songs that I like. Marble doesn’t even have a Wiki entry, yet Maebe Drive left such an impression on me that I’ll listen to anything that they do. I honestly, don’t know what it is, but there is something enchanting about this song that once it starts playing, I can’t stop listening to it.
14. Honey Bee – Plastic Smile ~Nijiiro Guitar Version~ (Canvas 2 ~Nijiro no Sketch OP)
No question to go with the Nijiiro Guitar Version on this song. I wouldn’t say I’m a huge fan of YURIA’s vocals, but when she sings a good song, it’s 99% of the time a VERY good song. Blame my mid 1990’s alternative rock roots, but songs that go from clean verses to distorted choruses are awesome. It’s catchy without being too poppy and aggressive, but not too heavy.
13. Mizuki Arisa – Kaze mo Sora mo Kitto (Sailormoon Stars ED)
I love Sailormoon. I love the music from Sailormoon, so it was actually pretty tough to pick a song. Pretty much anything from S, SuperS, and Stars would be a worthy pick. Even Moonlight Densetsu (DALI or Moon Lips versions) are favorites. I actually had the Sailor Stars Song listed here originally. However, I went with the Stars ED song. The song was perfect as the Stars ED and really meshed well with not only the ED sequence, but that season as well. It’s a song I can back to an listen to, no matter what my mood, and still enjoy thoroughly. There are a couple versions of this song, but I prefer the second version. By the way… the Moonlight Densetsu links were from the second R OP and from S, respectively.
12. Tokito Ami – Kono Namida ga Aru Kara Tsugi no Ippo to Naru (School Rumble Ni Gakki ED1)
It’s funny that I love this song so much considering that I don’t really care for Tokito Ami’s voice and was never a huge fan of Sentimental Generation (Scramble! 4TW!). However, when you pair this song with the ED sequence from Ni Gakki, it fits. A lot of people complained that the song was too serious and mushy to be a School Rumble song, but I personally thought it worked. Buried beneath all the jokes, misunderstandings, and curry is a simple love story–a love triangle (well more like a love hexagon). Slower and sentimental with a bit a gritty guitar.
11. Kawada Mami – Hishoku no Sora (Shakugan no Shana OP1)
Despite my infatuation with Get my way!, Hishoku no Sora is still my favorite song by Kawada Mami. I may even venture out there and say that it may be my favorite song by any member of I’ve Sound (I think I pulled a muscle there). In all honestly, I don’t think I would have even watched Shakugan no Shana were it not for this song. It’s a perfect example of a good OP song sucking you in. Take Kawada Mami’s melodic voice and pair it up with a great rock beat and a bit of piano. That’s a recipe for awesomeness.
10. Utatsuki Kaori – open (Tsuyokiss Cool X Sweet ED)
I think I’m the only person in the world that actually liked Tsuyokiss (I’ve watched it more than a few times). Mizuki Nana-voiced tsundere and tacky daikon jokes aside, open was an utterly outstanding track that I couldn’t stop listening to last year. It’s a great example of how a slower song should be done. It’s mellowness is what makes it awesome. There is complexity there, yet the tune is simple. It’s funny though, I associate this song a lot with fall and winter because it happened to be on one of the 2 mix CDs I had in my car almost a year ago. The rest of the CD sucked, so for most of November and December it was a Suzumiya Haruhi mix and open.
09. ROUND TABLE feat. Nino – Rainbow (Aria the Animation ED)
ROUND TABLE feat. Nino has done a number of good OP and ED songs (Chobits, Welcome to the NHK, Diebusters), but Rainbow really sticks out for me. The song does a great job of capturing the laid back mood of Aria, so it was especially fitting that it was the ED song. It was like everything good about each episode of the first season of Aria was topped off nicely every time Rainbow started playing. When you think about it, the song is quite touching and powerful, yet so simple–acoustic guitar, bass, drums, and Nino’s voice. Furthermore, the fact that this song remains just as good in the acoustic version is a testament to how good it is.
08. Shimokawa Mikuni – Sore ga, Ai Deshou (Full Metal Panic? Fumoffu OP)
I’m a fan of Shimokawa Mikuni’s music, specifically here slower stuff, but this song really takes things up a level or two. Like open, Sore ga, Ai Deshou does a wonderful job of staying simple, but bring a lot of emotion. The song manages to be powerful with it’s melody and music, but keeps honest with the soft vocals. It’s my favorite Full Metal Panic! song by far and another favorite that just doesn’t get old. Even Konata’s karaoke’d version sounds good, but I attribute that to the song not necessarily Konata/Hirano Aya. 
07. Sakamoto Maaya – platinum (Card Captor Sakura OP3)
We are now entering the realm of songs that are addictive like crack. Platinum gets the nod over excellent songs, such as Catch You, Catch Me, Honey, Groovy!, and Fruits Candy, for one reason. Sakamoto Maaya. I wouldn’t consider myself a huge Maaya fan, but I do enjoy a couple of her albums. It’s just a downright awesome song. Card Captor Sakura is my favorite series by far, but this song could have been used as the OP for some crap series like Sakura Diaries and I’d still listen to it all the time.
06. Kawabe Chieco – be your girl (Elfen Lied ED)
NSFW video… just thought I’d mention that. 
What better way to close out an episode filled with limbs being sliced off, blood squirting everywhere, and hearts being ripped out while still beating? Let’s just do a complete 180-degrees and have a catchy and upbeat ED song! One of the overarching themes of Elfen Lied was unrequited love and the song really does capture it. It’s your dose of cheerfulness so you don’t walk away ripping your hair out over an overly graphic and traumatic (yet awesome) show.
05. Younha – Houki Boshi (Bleach ED3)
I gave up on pretty all things Bleach nearly 2 years ago (back when Bleach was actually entertaining), with the exception of this song. There is very little to deny that Houki Boshi is a very catchy tune that was well composed. Younha has a lot of good songs, but I always find myself coming back to this one because it never gets old. Distorted guitar and piano make for some great music. Opted for the creditless, 5th Squad version of the ED for Momo.
04. Matsushita Moeco – Ame Agari (Angelic Layer ED2)
I think I have watched Angelic Layer all the way through only twice. I love the series, but it just something I’ve never had the desire to watch repeatedly. However, ever since the first time I heard Ame Agari around 2002 it has remained one of my favorite songs (even when I went through phases when I was rarely watching anime or listening to Jpop/Jrock). From the nasally guitar intro to strings during the interlude, the song is a great mix of stuff and quite the relaxing song. I’ve got many fond memories of sticking this song on repeat and letting it play for hours while I studied for exams, worked on papers, or drove home at night.
03. Kaitani Naomi – Tooi Kono Machi de (Card Captor Sakura The Movie ED)
Tooi Kono Machi de and Ame Agari, really go together in my mind, despite having really nothing in common other than they’re both from CLAMP anime series. Like Ame Agari, I’ve got a lot of good memories about this song; however, this one more so because it has been a favorite since around 2000. The song itself is soft enough to be relaxing, but powerful enough to really get you excited about stuff. Over the years, I guess I’ve developed a sentimental attachment towards this song because I tended to listen to it a lot when I had things going through my mind and/or was feeling down. It has this way of perking me up, even just a little bit. Great song.
02. Mizuki Nana – innocent starter (Mahou Shoujo Lyrical Nanoha OP)
Mizuki Nana possesses this amazing raw energy that really brings you to life. Not only is she my favorite artist, but she has a ton of great material that I could easily have selected for this list. Nevertheless, innocent starter gets the nod (even over Eternal Blaze, Nocturne, Hime Murasaki, and more recently Pray). If you think about it the song itself isn’t that complex, but all the power and emotion come from Nana’s voice. The song also does a great job to going from soft to heavy and back to soft throughout vocally and musically (listen to the transition between the chorus and the second verse). Innocent starter is an utterly addicting song sung by Mizuki Nana’s addicting vocals. It’s my #1 most played track for a reason.
01. Siam Shade – 1/3 no Junjou na Kanjou (Rurouni Kenshin ED6)
For as much praise I could give innocent starter, Tooi Kono Machi de, and Ame Agari, why would I pick something else to rank #1? Simple. 1/3 no Junjou na Kanjou is one of the greatest songs ever recorded. When I first watched Rurouni Kenshin back in 1999 or 2000, I was listening to a lot of punk rock and a lot of ::shutters:: nu-metal. Quite different from the simple hard rock that Siam Shade was about. Blame my early to mid 1990’s alternative rock roots, but I absolutely love the way the song is set up. Quiet and dirty-clean verses, distorted chorus, and a very cool whammy bar laden solo. I actually don’t listen to this song all that much, but when I do, I have to listen to it at least a few times. And every single time, I’m mesmerized by it. It’s pretty hard to put into words why I love this song so much. I just do.
wow, thats one great list you have there!~
should I be ashamed that the only song that I haven’t heard before was your #1 song because I never watched rurouni kenshin?… I think I should. =P~
Didn’t I already commented here? I said something about marble…oh well.
Great choices, there were three songs that I don’t know about, but the rest of the list is great.
I was 100% sure that ‘innocent starter’ was going to be #1. -_-
going through 15-9 i kinda was like “omg i don’t know any of these,” but once i got to 8 you had me smiling the the rest of the way through
i might have to copy you and do my own list!