cricket2, your suggestion is a very valid one, but I think that making it expensive to reduce how OP it is does not work; rather, it creates a more p2w scenario. To make it less p2w and less OP, I would suggest creating very limited ammo for such a weapon, so that each shot is more precious.
While on the button, I died from mega-pastry, and the screen got stuck to one side, so I can't see my elephant. Also, as the last best comments points out, the save and exit button doesn't work.
It was fun until I found that the Uzi couldn't hit some of the zombies that ran at the bottom of the screen, simply because it wouldn't point down there.
Can you have it so the cannon's appearance is changed after several upgrades milestones? So, when the cannon is upgraded past a certain point, it looks cooler.
At least let us be able to recognize camouflaged players on their team from the ones on our team, I ook several shots at one person before realising he was on my team.
 "Ballistic")
 "Achievement Unlocked 3")
 "Spy 2")
 "REPLAYING :the game:")
 "I Love Traffic")
 "Cerberus: Lord of the Underworld")
 "Z-Rox")
 "The Last Stand 2")
 "Socrates Jones: Pro Philosopher")
 "Loved")
 "Hippolyta")
 "Escape From 26")
 "Collapse It")
 "Diction"){kind=logo}
 "Learn to Fly Idle")
 "SHIFT 3")
 "You Find Yourself In A Room")
 "Idleplex")