GTA3, Putting in the peds have weapons cheat/peds hate you/peds fight eachother/all weapons cheat. Now that is some awesome and exciting mindless gameplay right there!

GTA:VC, put in the heavy weapons cheat, then equip the MiniGun and go to a crowded area(Like the Malibu club). Then fire away!

Twisted Metal 2, Put in the cheats for: Infinite Ammo, Infinite Turbo, Invincible and then play a small level(like stage 2 with max amount of bots)

Perfect Dark, play in a small level vs 8 Meat Peace sims, and use only explosive weapons.