There were 35+ techs at the Ford dealer I was at, and only 1 guy had an air powered rivet gun. I worked there for 3 months, borrowed it like 4 times. But I always felt bad because he was the only guy that had one, so people were borrowing it all the time. He was a cool guy though, and just used to bust everyones chops to get their own. Him and I were pretty good though, he was the main one that really talked me out of being a tech for the rest of my life, so I don't think he really cared when I borrowed it.
When I started off, I had to borrow tools ALL the time. But that was working at a Porsche place with 4 techs. The boss hired me knowing I had minimal experience, minimal tools, and told me to just use his. The stuff I used the most, was the stuff I bought first. Like an extra 13 mm wrench, extra 13 mm socket, etc. In a small shop situation like that, no one cared when you borrowed each others tools, as none of us wanted to have that 27 mm skinny wrench that we used once a month.
But, I started the "If I borrow it more then twice a week, I'll buy one" rule for myself. Not because I didn't want to borrow it, I just figured if I needed it that much, it was probably a good thing to own. I've got some special tools now that I never use, but maybe one day I'll be glad I had it.
Oh, and I still don't have the air powered rivet gun. I'm waiting for a project that I know I'll be putting a ton of rivets in, like a race car with sheet metal door panels.