Kurt Bowker has written a set of free wargames rules set in the Starship Troopers movie universe. I’m not sure where you would get the miniatures to go with these — perhaps Ground Zero Games has something that could be used.
rules
HALO Combat Miniatures Evolved
HALO Combat Miniatures Evolved is a set of free wargames rules based on the HALO science fiction franchise.
Three Musketeers Legends of the Old West Variant
Sgt. Perry’s Heroes offers a variant of the Legends of the Old West rules for miniature wargames set in the era of the Three Musketeers.
Solar Scourge Science Fiction Rules
Solar Scourge is a set of free wargames rules designed for 6mm science fiction miniatures.
Typhoon Modern Jet Combat
Typhoon is a set of free wargames rules for modern jet combat. From the author:
Typhoon is an introductory set of modern jet combat rules that does not require hex mats or any special flight stands for miniatures. It is designed as a quick playing, low complexity game for gamers who are interested in flying multiple aircraft with aircraft from the late 70s up to the Eurofighter and F-35.