I'm surprised no one has mentioned bearbangers.
For those not familiar with bearbangers, they're a noise making device similar to a shotgun shell that screws onto the end of a pen style launcher. After being fired the shell will travel 125-150ft and explode at 115dbs. I would expect bear bangers to be more effective than firing a gun, because the actual explosion occurs very close to the bear. Small, simple, cheap, and effective, I'd recommend them to anyone.
Pepper spray is a very effective deterrent; it's essential that there is no confusion over small canisters meant for protection in urban environments and bear canisters designed for use against large dangerous animals. People who are concerned about bear spray blowing back at themselves and their horse, I don't think are familiar with when its meant to be used. Bear spray is meant to be used against a charging animal at less than 25ft, it's a last ditch effort. I'll take the possibly of eye and nose irritation over inevitable teeth and claws.
Mountain lions and black bears don't scare me, but grizzly bears and moose terrify me.