I've mentioned my love of good Doom vids before, and I really like this because Doom Episode 1 is the one everyone has probably done (and still the only one legally free, since it's the shareware version), and certainly the one I know best.

A "stroller" run is one where you not only go as a pacifist -- no killing, although you can let enemies kill each other -- but also where you don't run or strafe. I wouldn't last twenty seconds doing this, but I love watching actually-talented people take up challenges like this.

One of these maps takes him over 600 tries, but incredibly, he (and one other streamer) do find ways to make it through eight out of the nine original levels. Really fun stuff if you were ever a fan of the original Doom.