ZDoom

Parallelepiped or cuboid, if be more precisely.
Because when there is a need in more or less flat actor it need dance around cylinreds with radius/height equal to 1.

GZDoom does not support cylindrical hitboxes, so this feature is already in. The opposite has already been denied.

What? Why wiki dead silente about this?
How I can make ideal cube actor?

All actors are already cubes. They're unable to be anything else.

Well they're more properly prisms with a square section, since their height is separate from their width.

Worth noting that they're always AABBs, too - The collision box doesn't rotate with the actor's rotation.