Cleaning the System is a platformer where you jump through levels as some kind of pogo stick. The movement is really fun and if you bounce well you can build up a lot of momentum, which lends itself to speedrunning.
There is also a free version of it from the GMTK game jam where it placed very well
But how about the Infinity matter dominator sword mod? It contains some of the most convoluted and basically unachievable crafting recipes Ive ever seen, just scroll down and enjoy the ride
I recently heard of odysee and was surprised to find out that some big channels like Veritasium or Fireship seem to already be on there