Sometimes I get jealous for the strangest of reasons.
One of these is when people say they haven't seen/heard/played something. My mind instantly goes - "hey, I want to be able to do those things for the first time too!"
Because I do. And if I could forget the experience of doing these things (and the related memories), I would. After writing a convincing note saying: "hey, do this thing you've never heard about!"
High up on my list of things to forget would be Lost (as I can't imagine watching it a second time), the Fallout series (that first time was quite an experience), and Godspeed You Black Emperor (twice). And if you for any reason has not experienced these - well, now I'm jealous again.
What would you want to forget, in the good sense of the word?