Documents for sure. Every school paper I've done since 8th grade is on my computer. Also all of my web-design invoices and history are on there. Either way though it wouldn't matter as I have everything on this computer backed up to my online server, as well as an apple time machine, and another imac.
pictures for me, almost everything is backed up for me and since most of my games are through steam they would be fine. Documents would be a big loss as well. But pictures are more important to me so yeah.
Pictures hands down. Documents would be a pretty big loss, but Quicken data can be re-entered and schoolwork can be redone. Music and programs can be re-acquired and the loss of a saved game just means I get to play the game again. Many of the pictures I have however are precious snapshots of family and friends that can not be replaced and do not exist in any physical form.
I was really torn between pictures and documents but chose pictures because they can only be taken once while just about everything else can be found again or redone.
I've had so many hard drives die I've lost count, after the twentieth drive dies you come to a zen like state where you realize nothing was lost, it was digital. it never existed. THAT said if my picks disappear i'm gonna me sad...
Well, if you're asking which would be most devastating to gaming/my computer in general, programs. Most devastating to my life would be my music defiantly. I. LOVE. MUSIC.