Luigi's Mansion theme song's pretty catchy, it's been ringing inside my head for quite sometime.
Also such tunes like: Super Mario Bros. 3 Theme, Endless Possibilities from Sonic Unleashed, The Underground Theme from various Mario games, different songs from Eternal Sonata, Tetris, Dr.Mario and so on. Pretty many known classic video game tunes are amazing...
There might be other cool songs, too but none's coming to my mind at the moment.