Metal Fight: I've worn down the gears of many a Hasbro Light Launcher to the point where many of them aren't usable. Hasbro made a pretty sad Light Launcher to be fair, and some of them came with poor gears anyways. What really made me sad was my Japanese Light Launcher, which I shattered the hold parts on (and should probably replace them). I also succeeded in breaking the handle of my L/R String Launcher, and although I can still pull the string with that tiny little knot at the end, it's hard to get a solid grip and pretty painful to do after a short time.
I've had a few part breaks too, mostly with smaller tracks and bits from MFB. I know I split a 100 track in two, and numerous other tracks are missing those little extensions on one side. The amount of face bolts I have that are worn down or completely broken is almost impressive, although fortunately my metal faces are in great condition. I also managed on shattering a Flat tip, but i've got so many that it's really not worth much.
Burst: After an incredibly awkward launch, I snapped my Long Winder clean in half after an aggressive launch (which still launched properly despite the break). I similarly broke my Sword Launcher's ripcord, sending the grip flying into a wall as the stick just sat inside the launcher sticking out awkwardly. Fortunately it was around the time the Digital Sword Launcher came out and now I'm using that, but I've had it in my mind to replace the regular Sword Launcher as I have a lot more control with it.
Beyond that, the Burst line has stayed a lot more solid than MFB, with the only really notable part damage in my collection being a sizeable dent in one of the wings of Hasbro's Roktavor and a small crack in my oldest Survive tip from TT (ironically from Ragnaruk). Beyond that and standard tooth wear, they're pretty solid.
Cincinnati-based Organizer, and owner of every single currently released TT Burst bey part in at least one color. Hard to think of anything I don't have from MFB either...