pneumatic grease guns are good fun, one workshop I worked in had a reel set up that pumped from a 44gal (205 liter) drum of grease which was outside. On a hot day with the grease heated by the sun you could shoot it all the way across the workshop!
Another trick was to wander up be side one of your workmates and carefully drop the nozzle into the pocket of his overalls and pull the trigger, filling his pocket up with grease without him noticing!
I have an ancient pneumatic grease gun that's Australian Army surplus, I was told they were used in the workshop for Centurion tanks, it has an unusual double swivel head and is great for those hard to get at places, it also is the most powerful grease gun I've ever used. It gets grease in with ease where others give up the ghost.