Walker was great, and I spent a long time playing the demo of Qwak, not sure if that was out on other platfroms tho...
Can't beleive no-one's mentioned Payback yet?
Before GTA3 came out on the PS2 I had friends coming over and getting me to let them have a go on it, now that's the kind of games/app needed if there's going to be any kind of resurgence in interest in the Amiga..