My favorite are randomized speed runs, where everyone gets the same randomized version and have to speed run it against each other. Normally these are done as real time races and the results of the randomization aren't known to the player until they start. Not all games support it (think games like Zelda and Metroid where you have to collect powerups to push get past obstacles to collect more powerups to get past more obstacles). The randomizer has to make sure the game is still beatable (so no locking a required item behind an obstacle that requires the item). It is also an area that TAS can't help and it has more to do with strategy than physical perfect button presses. Also, since every time you uncover a new randomized item it changes what is the most potential optimized path, it require a deeper knowledge of the game compared to speed running where there is normally a given optimized path that people compete against.