Some of the G1 Constructicons' guns have some very thin places, and Tonkanator's components are packaged in a plastic try that's designed so that parts "snap" into place and are held securely without need for an upper layer. This is a bad combination. Mega Hauler/Long Haul's gun just effortlessly folded right in half along the groove sculpted right across the middle as if specifically for this purpose, and I feel like it'll probably break the rest of the way if I look at it funny.
This is the only one I had an actual problem with, but all of them except Mega Dozer/Bonecrusher's have places that look worrisome.
I don't have the "Vintage G1" Devastator, but he appears to use the same packaging, so if you're opening up one of those for some reason be careful with him, too.