Looking for an alternative to Warhammer 40K? Who isn’t? This may be it. Even better: these wargames rules are free. Ivan Sorensen’s Fast and Dirty rules also would work for modern combat.
Game Workshop’s Space Hulk game is one of the best it’s every produced. Every game is fraught with tension, as the marines attempt to maximize their scarce action points in the face of an increasing onslaught of genestealers. With good players, this game is nearly always a near run thing. Unfortunately, like so many of their efforts, the Evil Empire hasn’t continued to support it. Expanding The Hulk is a website dedicated to continuing the Space Hulk game. It’s got rules for using many of the other races in the Games Workshop universe, including Chaos, Eldar, Dark Eldar, Necrons, and Orcs.
Given the absurd prices on Warhammer 40K Titan models, this paper model of a Warhammer 40K Chaos Warhound Titan may be just what you needed.
Graven Games has a set of counters for Warhammer 40K Sixth Edition.
Stargrunt 40,000 is a system for converting Warhammer 40K army lists into a format usable with Stargrunt.