Vampire The Masquerade Bloodlines does not have Z-Block because unlike all other Half-Life 2 based games: their dev went under and thus has never updated it. So you can easily bhop around all the levels really quickly. It's how I always got around the hubs in that game, because it's a more fun way to travel, it's a fair deal faster, and I always thought it was hilarious to have a super powerful vampire basically skipping around the city like a school girl.
The original Day of Defeat had a bug, that I don't recall ever being fixed(although you could get banned from servers for it.) You would lie down on the ground in prone position, and then hold down a strafe modifier and push your mouse forward as fast as you could repeatedly. You would slide across them map faster than you could possibly go by sprinting/running and all while in prone position. It frustrated the hell out of snipers and let me flank the enemy repeatedly and easily every match.