The mission of U4 is to present 4th EDITION D&D rules for use in non-fantasy settings. These include pre-modern settings, contemporary settings, and those that are far flung fantastic and futuristic. U4 is perfectly suited for any of these following campaigns:
Wild west, with or without aliens
U4 has no included setting, allowing you to explore the rules in whatever context you wish. The rules are offered in a general way, not assuming any time period. The equipment lists a wide range of various firearms. Though most are modern, there are quite a few that are retro and futuristic.
The new "Ladder" system which offers more adjustability with character creation. Modify your class with one of seven ladders.
Eleven new classes including sniper, faceman, infiltrator, and the grappler.
New armor including powered combat suits.
New skills & feats.
All new weapons including traditional firearms, rocket launchers, and laser rifles.
Pimp your auto. Purchase vehicles and modify their features.
All new opponents from fanatics to tanks.