What part(s) have you let go, only to wish you had kept them not long after?

70 440 HP2 standard bore short block, I had it on an engine stand sealed up for about 10 years. A friend & his cousin came by one day, we talked about it & the cousin made me an offer on it. The offer was much more than I had in it, so down the road it went. I got a call from my buddy & he told me his cousin managed to kick the crankshaft & 3 rods out of it two weeks after he got it running in his GTX. Apparently the cousin was a few fries short of a Happy Meal & really enjoyed seeing how high he could wind engines before she scattered them.