I like a lot of OPs/EDs, but I've finally narrowed down my absolute favorites so far.
Paranoia Agent OP - Yume Shima Shinen Kouen (RAAAAAIIIIIYA IIIYO)
Ano Hana ED - secret base ~Kimi ga Kureta Mono~ (KIMI TO NATSU OWARI ;_;)
I don't really remember much OSTs (unless they're from a VN) for some reason, but Clannad, Sayonara Zetsubou Sensei, Kaiji, and Madoka are honorable mentions. And Susumu Hirasawa.
Paranoia Agent OP - Yume Shima Shinen Kouen (RAAAAAIIIIIYA IIIYO)
Ano Hana ED - secret base ~Kimi ga Kureta Mono~ (KIMI TO NATSU OWARI ;_;)
I don't really remember much OSTs (unless they're from a VN) for some reason, but Clannad, Sayonara Zetsubou Sensei, Kaiji, and Madoka are honorable mentions. And Susumu Hirasawa.