I've chased away my lazyness for a while and managed to get my entry done, sort of.
I hereby present to you:
Reflex.wad
Description:
With mouselook and strafe available to us, most of the original doom monsters didn't prove to be a challenge, but with this wad, that's about to change. The monsters have become agile and dodgy, some of them will even jump at you, if you are close! Most monsters will now have less delay before attacking, arachnotrons will prove to be a threat this time.

The enviroment now acts a bit more reallistically - explosions shake the ground as well as the biggest enemies.
Pinkies *cough* I mean demons are now not-so-pinkies, they've been blessed with a slightly darker skin, how tough they've become just didnt go well with that colour.

I've left the archvile, bossbrain and former humans untouched, every monster has the same amount of health as before.
All in all, this mutator is aiming to raise the difficulty of gameplay, while staying quite loyal to the original monster code.
(No random recolors of monsters throwing excessive amounts of projectiles at you! Also no cheap bestiary copies)
Tip: Keep your distance. I mean it.
Your reflexes WILL be tested ;P
Download link:
http://www.speedyshare.com/401976578.html