Very Nice
Enjoyed it very much, two suggestions:
1. Have it end damnit, I don't know if there is a last wave, because after level 60 or so (if I make it that far), I get bored and stop playing - would suggest you have a game mode where you can actually win after about 50 levels or so
2. Actual data on how much damage weapons do would be nice. When I play, I am not sure how much damage a machine gun does versus an acid gun etc. As it stands now, I have to guess as to what works best.