What are some zdoom effects that are rarely used, & which wads have you seen them in?

I was thinking of this while playing a couple of train levels. They don't seem to be used a whole lot, nor are voxels, or portals (where you're able to see the actual destination from the origin side).

I've used a ton of vertical portals in my DMP2012 map, The Space Base, in order to make it look right.

Not sure if this is Zdoom specific, but I've never played a proper wad with room-over-room buildings.

I'm watching this thread because I'm actually pretty uneducated about the good things about zdoom, not including good things that are good for zdoom users and viewed as bad elsewhere.

I noticed that polyobjects aren't used quite as much as they could be, it's mostly for doors and spinny things in the background.

MajorRawne said:

Not sure if this is Zdoom specific, but I've never played a proper wad with room-over-room buildings.

Check out these ones:
Winter's Fury - immersive quality GZDoom mapset.
1024 x 1024 The Building - amateurish, but kind of cool short mapset.