Alien Hominid is a run-and-gun game where you are an alien trying to stop the FBI from killing you. The gameplay is similar to that of Metal Slug, where there are endless amounts of enemies and you're just firing like mad.
This game is very well made though, so good in fact, that you can buy a Gamecube, PS2, Xbox or an Xbox Live Arcade version. The consoles levels are completely different and significantly easier. The two-player co-op in the console version is the real major difference, which prompted me to buy the GC version a couple of years ago.
The flash version is relentlessly hard but, once you get a hang of the controls, you'll be taking out FBI agents in no-time. Pressing down and the jump button when you're above an enemy will help you out a lot as you'll latch onto someone's head, freaking out any other FBI agents nearby, giving you a free shot. Otherwise, just keep moving and shooting and you'll hopefully make it through.
To play Alien Hominid, click on this link.