Unreal Tournament 2004 had amazing vehicle combat. It's multiplayer is pretty active still, but the bots in that game are just as good if not better than most human players if you can't find any. Stick them on Godlike and you'll get ruined.

Red Orchestra?

You might not be able to run it, but Rage is decent and there's a pretty heavy focus on vehicular combat.

Try Battlefield 1942 or Mechwarrior 2.

>>5211
battlefield 1942? do people still play that? or are you saying he should play the AI (which iirc are really bad)

Battletanx

>run in somewhat old hardware
Choplifter!