Robocraft Griefing, by Angry Diplomat

Earlier in the game's history, they had just finished boosting the cost weighting of tougher armour to reduce the prevalence of near-indestructible tanks in some brackets, and people actually had to choose between powerful guns or tough armour to some extent instead of just loading up a smallish cube of hellishly resilient blocks and plonking a single huge cannon in the middle. This led to a lot more experimentation and somewhat better balance, until someone figured out you could simply bolt the biggest fucking gun you could get onto your cockpit and have a robot with two parts: a gigantic cannon and the screaming pilot strapped to said cannon. They would use the weapon's recoil to propel themselves and essentially zip through the air on barely-controllable laser-fuelled rocket ships, occasionally one-shotting opponents with a well-placed zap as they spiraled overhead at Mach 4.

I got into the game just after that little exploit got nerfed. The bigger guns had their recoil considerably reduced, and if I remember right, it was no longer possible to weld a weapon directly to your pilot's chair. It seemed the gunchair was a thing of the past... until I figured out that, by attaching my cockpit to a little line of three or four blocks and clustering a handful of moderately high-powered, downward-facing, rapid-firing laser turrets along the outside faces, I could create a new iteration of the gunchair: the LASER TORNADO.

When you have a bunch of the same gun, holding down the fire button chain-fires them continuously, one after another, at regular intervals. The right gun, in the right quantity, balanced against just the right amount of weight with just the right distribution, could chain-fire in such a way that my little armoured sofa began to spin at increasing velocity, steadily building up momentum as it whirled forward atop a wake of projectiles like some unholy marriage between a helicopter and a terrifying airborne squid composed mostly of lasers. It would continuously gain speed with no apparent limit as long as I kept it pointed in more or less the same direction, and its shape was such that it would ricochet madly off of terrain without slowing down much at all.

Enemies would fire wildly at air as this little asshole spaceman on a gun-encrusted demon couch flew/ricocheted/screamed past them at normally unattainable speeds in an obnoxious clusterfuck of PEW PEW sounds, hideous grinding metal-on-ground noises, dust clouds, and wildly inaccurate laser blasts, until the sheer volume of projectiles finally sheared a wheel or gun or something off of someone (or scored a lucky hit to the cockpit and killed them outright). Meanwhile, my teammates would trundle up in their dickmobiles and giant flying swords and goofy little space rovers and start shooting the enemies in the ass while they fishtailed around trying to target me in the quarter-second before I slammed into the edge of the map and ricocheted around for another pass. Sometimes I would ram into enemies and flip them over, then spin in place like a douchebag hovercraft before PEWing away into the sunset (read: the enemy base, where I would sit around scoring capture points until they rushed to stop me, then howl away in a storm of lasers and hysterical laughter).

It was not a very effective design - I didn't get a lot of points - but holy fuck was it ever fun as hell to play, and I used to get quite a bit of rage in chat.