Well since it's a question on favorite tool, I would have to say my old Gerber multi tool (Leatherman style but I like it better then the Leatherman).
I usually bring my M-Pro7 cleaning kit with me in case of a stuck case or needed oil.
I would love to get a spotting scope, but the range I go to rents them for $2. So, I can't justify spending $60 for a crummy one, much less $$$$$$ for a good one. Their old beat up rentals work good enough for my skill level. Hopefully one of these days I will be able to improve my skills to where a good spotting scope is needed...