Hey. I didn't do much to this so the credits go to Dunk (Creator of the original Prop Cannon) and Lexi (Updating it to the new GMod update and making it work with Wire)

All I did is just fix the Right Click bug which gave a LUA error when you tried to select an object for ammo. It works fine now.

There are still a few bugs that I'll try to fix which Lexi skipped over ;)
- Delay option doesn't work.
- Using Recoil above 0 might explode the "projectile" at the same moment as you fire it.
- If the Prop Cannon is too close to the object "holding" it give the same result as above.
- Projectile weight?

Quote with info about the addon from Dunk:
The Prop Cannon stool lets you place mobile cannons that can be attached to contraptions. The cannons can fire any type of prop, and you can set how explosive the projectiles are (if at all).
Great for traps, defences or as weapons for contraptions such as tanks, planes and ships.

Quote with info about the update from Lexi:
Can be wired with the Wire mod

Original Outdated Prop Cannon by Dunk: http://www.garrysmod.org/downloads/?a=view&id=2693
Updated version of the Prop Cannon with the wire function by Lexi: http://www.garrysmod.org/downloads/?a=view&id=106851

Tell me if there is something I forgot ;)