This is The RED GOLDEN DRAGON CANNON Made by ZinoZack47
thread:
http://zppv.boards.net/thread/28

if you want the dragon cannon weapon icon show up when killing a zomibie go to your sprites/hud.txt
look for
d_headshot				640 640hud1 0     240   36    16
and paste this under it
d_cannonex		640 640hud40	172	176	48	16 

Enjoy!!!