I used to be all about the old school NES games and had emulators and roms up the wazoo before losing them in the big reformat when my comp got infected.
Then I had my XBox modded and got emulators with every NES and SNES game ever released in the United States and a few that were exclusive to other countries (mostly Japan) on it.
In addition to that, I can now play DVDs on the XBox without paying $30 for a remote (imagine, just like my PS2. Suck it, Microsoft!) and the start-up and logo are bright blue instead of the usual green. With the flip of a switch, the mod chip is turned off and everything acts like a stock XBox.
I could use the mod to cheat at games (HALO and HALO 2 being the only games I have for XBox, and as far as I'm concerned, the only reason for its existence), but I'm not really into that.
Plus I don't really know how.