All of the above, bar porn.
Then again, I've got a number of external drives. Anime, games and Wii games on a 1.5TB external, and everything else that needs storing on the 2TB RAID NAS. Work on a 1TB external, aswell as copies on my flash drives, and portables apps on my flash drives too. One 1TB external failed (damned SeaGate), so I'm not sure exactly how much I've lost (aside from most of my Wii games) but everything else still works. I've even got a RAID enclosure spare (after getting the RAID NAS).