40K Unlimited is a set of fan created alternative rule for Warhammer 40K.
Rules: Games Workshop
Ninth Age Alternate Warhammer Fantasy Rules
Given the general fan anger over the direction Games Workshop has taken its Warhammer Fantasy property, it is no surprise that fan written alternatives have cropped up. One is The Ninth Age, a a set of free wargames rules for playing mass fantasy battles. It looks very well done, and has a large number of army books.
Age of Sigmar Point System Fix
Age of Sigmar, Games’ Workshop’s attempt to kill Warhammer Fantasy, lacks even a basic points system. The rules allow each player to field whatever sized army they like. That doesn’t sit well with a lot of players, so the One Page Rules guys have come up with a points system fix for Age of Sigmar.
One Page 40K Chapter Lists
The One Page 40K Rules have been updated to include lists for various Space Marine chapters.
Activation Roll, Action Point Alternate Skirmish Rules For Warhammer 40K
Gemini is a set of alternate skirmish rules for Warhammer 40K that use an Activation Roll, Action Point system.
There seem to be quite a few people who love the Warhammer 40K Universe, but who are less than enamored with the rules.