Super Crate Box

It's been out for a couple years and I still play it in my spare time.

Great for when you're downloading a particularly large file, waiting for someone to get online so you can play something else, or just in the mood for some good old fashioned fun with games.

Goal is high score. You pick up weapon crates to boost your score. Killing enemies does nothing but make your life easier. Every time you pick up a crate you're stuck with a random weapon. There are some unlockable weapons/skins to make the first few games more exiting, but the real fun starts when you unlock SFMT mode. And no, I don't know what it means.

Oh, and it's free.

http://www.supercratebox.com/

I find this game extremely hard.

If it were easy it wouldn't be fun.

Edit http://www.supercratebox.com/?p=highscore&level=1&diff=3
Look at 18th place, or lower should you check a while from now. I got a high score and I'm damn proud of it.