Oops, not sure what happened with my previous post, I somehow deleted part of it. It was supposed to say 'favorite weapon.' But yeah the rifle was cool too, especially with the upgrades.
I may slowly go back and try to find the things I missed, not sure if I'll bother to get 100% though cause you're right, some of the challenges and GPS caches are a pain to find. Maybe I'll cheat and watch youtube videos of the locations.
DEFINITELY look up the locations if you're stumped - otherwise you'll drive yourself crazy! I did still encounter a little combat, so that was nice.