A game I used to play:
I remember it being called Clayland, but tried google it for ages with no result, so maybe it was unpopular or I remember the name wrong.
It was a game with top-down view. Shooter. You spawned in the middle of the screen, and had to pick up weapons such as shotguns and all the way to plasma guns (which would bounce from enemy to enemy). The enemey was zombies, in later stages the levels would get really hard, with zombies ALL over the place. I also remember it as there would get other enemeies besides zombies, such as big insects, but Im not sure. There would also spawn white worm looking "hives" which could spawn zombies and other enemies directly on to the field.
The graphics were really simple. Just plain 2d, no 3d.
I played it around 2003-2004.
Your help is much appreciated.