An inexpensive one: I bought a couple of cheapo old SCSI hard drives from TradeMe (NZ's eBay equivalent), and they arrived without the terminating resistor packs. The seller was kind enough to send these on when I queried it, but he unfortunately just stuck a few in a standard envelope... End result: envelope containing snapped pieces of resistor packs!
I guess it didn't occur to him to tape them to a bit of cardboard first! D'oh!!!!
- Ali