On summit you can jump up and over a wall in one of the spawns and get onto a roof that looks into enemy spawn with a lot of invisible walls on the top.
On Farmhouse push when this is point A, you can jump over the barrier in this image, but you can't jump back over it. this locks you outside of the map.
There's a stone step path leading down (or up I guess) on Summit with a rock that has no hitbox. You can stand inside this rock and shoot out of it and people cannot see you.