Father's Day, anyone? Memorex has created this device for that technologically savvy money clip user. It is a flash drive that can also double as a money clip. It is available in capacities in up to 1GB and is available for $35 at Target stores. It may be a bit bulky for a money clip, but think of how impressed the strippers will be when your dad is "making it rain" from bills coming out of his Memorex flash drive money clip.
It won't run Doom per se, but it will STORE Doom and allow it to be played as a portable application as long as you can open a DOS window somehow.
But don't be a shmuck, if the machine can run portable apps from flash drives at all you should be running Quake 2.