Under Defeat is a vertically scrolling shooter where you can pilot a helicoper against ground, air, and sea forces.
Ultimate Fighting Championship: Tapout
On its own merits, UFC: Tapout is an excellent, original fighting game that's especially fun for two players.
Ultimate Fighting Championship
Ultimate Fighting Championship for the PlayStation doesn't have anything to offer beyond the good name of its Dreamcast counterpart.
Unreal Tournament is the most complete first-person shooter available.