Ooh! Fun update.
Keyboard movement has been HALF fixed. When you press another key while moving, it still glitches you into perma-moving in a direction, but pressing any key will stop this now.

Bullet penetration options have been added; there's a % chance that bullets will penetrate zombies/players (but not walls), set to 50 in the Engine class.

What I forgot to mention last commit: Dev stats have been added to the HUD over the Game Window (FPS, Memory Usage, and # of Objects sent/received aka "Network")