In Q3, it was more the way jumping impacted your movement speed which was a discovery. Another example would be the Tribes series, with skiing which was also an abuse of the game physics (and taken as the main movement mechanic in the latest game, Tribes Ascend).

It's nice to see such parts of gameplay emerging from simple bugs. I would argue that it's much more rare nowadays, with games which aim to be always more realistic, and blocking your movement.