Mines one of my hard drives, a 250Gb Samsung Spinpoint SATA, been in 4 builds, closly followed by my trusty old Plextor DVD writers, an 8x PX-708A now in an external housing and a 16x PX-716SA SATA drive.
Bit of kit that I bought the longest ago is my TDK DVD writer, bought late 2004. It didn't actually go into the machine until spring 2006, along with my current case, floppy drive and motherboard (939Dual-SATA2).