You've got the usual Bionicle Mafia, although these days more often than not every game has its own unique twist that modifies how you play the game.
Steal the Mask, Pool of Protodermis and Last Letter Game, all of which have remained active ever since the Downtime in 2011 (the first now with a sequel that is a paradox of existence). Don't forget Image Chunks, which recently resurfaced for the first time in two years.
Bionifight, with a fifth installment that has altered the way Bionifight games are played, while also finding new ways to involve players in the creative process - and also making its first appearance in two years.
VERSUS - a brand new game based on the concept of a series that was last seen in 2009, and What Could Go Wrong?, a brand new game just about to begin.
The Music Game and Snappy Comeback, both building on the basic ideas of how you play games like Last Letter Game and twisting them into newer incarnations.
There's Technic Coliseum, another unique fighting game with a sequel that will change the way the game is played in the works.
And of course, Hitman, which must be played and experienced to truly appreciate (it combines some aspects of Mafia, tabletop games, and outrageous humor for one of the best experiences you will have on the forum).
I recommend you take a look if you haven't already - chances are something there will work for you.