Door stacking using the RCD.

[Erik]

You can easily stack multiple doors on top of eachother, this is pretty powergamy and can easily be abused this can easily be resolved by checking if there already is an door on the floor.

[BlackPhoenix]

I don't think you were looking for powergamey. Shitty? That said, opening a door to another door is a very Ss13 type gag

[Cirrial]

The first time I came across this as an obstacle I actually loved it. It wasn't hard to surpass and felt very, well. (5:30 in, apologies for terrible video quality)

[Roomba]

Yeah I'd call it a feature, it's more funny than actually malevolent and as far as obstacles go it takes a lot of time and resources to build and isn't especially difficult to bypass.