talismoon fan replacement, case mods, dvd drive case mods, southpaw controller mod, rapid fire controller mod, change smd led colours, dual boot nand, 360 nand downgrade. a couple of early emulators the snes and mastersystem ones. dev kits have the ability to run full mame emulator amongst other things. cant think of anything else at the moment.
As well as GS modding, and game modding such as Halo 3, and before it was patched, CoD4 and CoD5 multiplayer modding. I think single player + co-op mods still work though.