Just saying that the original idea was from Lance who told me that he was going to do something similar and it interested me

Basically what it does is adding simple player movement prediction for classic Doom monsters (Imp, Baron/Hellknight, Revenant, Mancubus, Cacodemon, Arachnotron, Cyberdemon).
There are minor visual modifications to the monsters as well as changing speed of monster projectiles to constant 15 for these that have normal speed of 10 and fastmonsters speed of 20.
Demo of pretty tough cyberdemon:
Download: http://www.mediafire.com/download/v8317 ... rtmons.wad
Works with ZDoom 2.7.1 and associated GZDoom, also works with Zandronum 3.0. ACS sources included.
Everyone can abuse the code for whatever reasons they want. Enabling prediction for your monster is generally as simple as copypasting existing A_CustomMissile code.