One of my favorite miniature wargame rulesets is Fast and Dirty (F.A.D), a free, rules-light ruleset which is officially, sci-fi, but could definitely be used for WWII and anything beyond (cold war, modern, near-future, cyberpunk, post-apocalyptic and sci-fi). It could easily cover a wide range of settings and technologies, as its weapon definitions are a bit abstract and so can fit a wide range of titles. It uses only d6's and can be used for both the 15mm and the 28mm scales. It works for anything from a few squads per side to company-level battles.
You can find F.A.D 4.0
HERE. A discussion forum is available
HERE - feel welcome to join the discussion if you're interested in F.A.D!
By the way, F.A.D 5 is in the works!