Jim and Yahtzee doing goofy mini challenges and making fun of each other all the while? Subscribed!
Also got a few possible challenges for you:
Goat Simulator - Most goat modifications (devil, jetpack, halo, hat, etc) or highest score; either would work.
Painkiller - Most kills using only the painkiller's laser beam on the level of your choice but you cannot move to adjust the beam after it attaches to a surface; you have to try and orient it so enemies run into it and kill themselves. You can recall the painkiller to attach it to something else, but when the beam appears no moving is allowed
Max Payne 3 - Most breakable environmental stuff shot while diving in slow-motion.
Octodad: Dadliest catch - In the grocery store, most items fit into a shopping cart OR in the house level, remove all balls from the shed and then put only soccer balls back into the shed, 1 point per soccer ball, -1 for every other.
Dynasty Warriors 8 (the only one on steam I believe) - Most kills, but the only way you can move is by using attacks, no WASD or analog stick or anything like that.
Just Cause 2 - I don't know what would make a good challenge, but the grappling hook must be involved. Maybe attaching a car to a plane and seeing how many people you can hit with the car like a wrecking ball? I haven't played that in forever, so I don't know if that's something you can do or if the car will just snap off or you couldn't fly the plane at all.