I'm not sure if this could count, because its more of a issue with objects themselves...
I sought out to create a old-school type of platforming game. I got it to partially work, but left it alone because of frustrating limitations. One being that if you stand on a box (I made it really big) and you give that box a vertical AddPropImpulse, you would simply fall right through it. But if I gave it a X/Y movement, you would be alright...
Other little scripts like AddAttachedPropToProp should actually work also.