I survived for 93 seconds. Wave 3 is hard .~.
Cool little game made in Scratch. Enjoyable, cool and simple gameplay.
I'd say to change the way the weapon switching works.
Changing weapons with 1,2,3 isn't the best idea in my opinion. You could have used just 1 or Q, like you do in Call Of Duty and Counter-Strike
Idea: get points by killing zombies and buy more superpowers:
Freezing zombies
Exploding Bullets
Shield
S P E E D
e.t.c.
Good Job!