I wish that too. In particular, I'd like to wipe Mass Effect trilogy from my memories, at least temporarily. It had huge emotional impact on me, and I would love to relive it all again - unfortunately, I still pretty much remember the entire plot after the years (and though ME has some interesting degree of non-linearity based on your in-game decision, there's still too much of the plot that's constant to really enjoy a replay without a memory wipe).