Just like the amazing amount of StarCraft glitches, ranging from making ground units fly to completely insine stuff like turning a unit into a trap that crashes the game for every player who looks at it (and after some time crashes the game for everybody). All by legal in-game actions. I can't find a link, but one comprehensive summary back in the old days suggested that at least some of those glitches may be intentional, given how improbable, weird and useful they were.

Anyway, an example list: http://www.entropyzero.org/Glitches.html.