I've heard a few of the bands mentioned before, but I'm surprised no-one mentioned the Pillows yet. Been around for ages, and have one of the best back catalogues I've come across for a while.

Advice - Punk-y type rock
One Life - Makes me think power ballad for some reason =P
Ride On Shooting Star - Happy rock

Just look for the FLCL soundtrack, they did most of the songs off that