These are my redesigns on 'Mr Door Stopper' by Roland.

I didn't print the V4 because I already had a better idea before I sent it to print.

The first file has notches like a regular doorstop, but they are the wrong way around, so don't print this file.
V2 has the notches the right way around, so this one is the closest to the original Mr Door Stopper, but with the notches.
V3 is V2, but the head is flattened for faster and nicer prints.
V4 is V3, but with a bit more taken off the top for even faster prints.
V5 is V4 but has a steeper incline, allowing it to fit bigger doors. (has less grip on the carpet because of fewer positions per cm of height.)
V6 is V5 but 42mm tall rather than 50mm of V5 and has a narrower base for faster prints. (it still works just as well.)

Which one is for you?

Heavy doors: V4 or V5 (Low gap or high gap)
Big doors with high gap: V5
Small Doors: V6
Medium doors: V6
Fastest Print: V6
Strong: V4 or V5 (Low gap and high gap)
Best all-around: V6
Closest to the original but still has good notches: V2