Easy Challenge And Achievement:

Back on Borderlands 1, there was a claptrap behind Marcus's store in Fyrestone. In Borderlands 2, go to Fyrestone and find the store. This time, you need to jump on the mailbox, and then jump onto the awning. From there, get on the roof. The claptrap will still be there (he's dead though). Jump over to him and take his chest of guns for free guns and a challenge. Also in the area, if you go to the spawn point of Saturn (the big robot/loader) and look toward the Hyperion building and turn left, there will be a building. Go to the building, jump in top of a few items until you're on the roof. Then open the chest. Easy 15 gamer score.