Ohh dear..A bit too many to decide upon..But I suppose..
Inuyasha: My Will, Fukai Mori, Every Heart
Rurouni Kenshin/Samurai X: Yoakemae, Dame, It's Gonna Rain, Ice Blue Eyes
Cowboy Bebop: The Real Folk Blues
Gundam Wing: Just Communication, White Reflection
Shaman King: Trust You, Northern Lights, Silent Weapon, Omokage, Brave Heart (wow there's a lot for that one..)
Slayers: Midnight Blue