I broke many parts for use but the 2 most i felt sad was a BBPegasus from the DX Set wich make honour to its name: Big Bang and all the pieces "explodes" in a battle; that was due to a defective inner screw in the spin track. (all in all it was espectacular).
The other was a TT L/R beylauncher wich is for me the better i use, luckily i found another at a good price.
In the last months Hasbro was selling the old double packs of MFB, considering that was manufactured and putted into the blister many time ago, suffering temperature changes and, the most important according to the Beywiki, these beys are the ones with most of the old molds wich brokes, Dark Bull horn spin track, Dark Libra spin track and many other defective MW, is not rare that some people has been surprised for this and suffer it.
I have some of them and can comfirm that brokes easily.
Be care with these old set of 2 beys from Hasbro; too much time inside a blister to work well and some of it faulty or wrong.
Salute!!
EDIT: the Hasbro double packs was sold a year ago or more, but in countries like England, France, Italy, Spain.....appears again and as a "quit-of-old-stock", tons of them before summer till these days; just for clarify.
Part of my Bey collection and other Bey stuff:
http://www.youtube.com/watch?v=eAkmqy1OPqw