Steam has had a lot of deals this weekend, most of the others have been posted and I thought this one deserved some recognition too.
From a distant corner of the galaxy, an evil alien race sets in motion a sinister plan to conquer the Earth. They unleash a powerful catalyst Energy X that imbues the planet's worst miscreants with super-powers to bring the planet to its knees. Now Earth's only hope lies with a new breed of heroes... The Freedom Force!
Command a squad of comic book heroes in the defense of Patriot City. Choose from over a dozen heroes or create your own comic champions. Fight for freedom in over 20 action-packed missions. Restore order in a completely interactive 3D world. Take your heroes online and join the fight in multiplayer mode.
Getting on a bit now but both still highly rated. They're age is actually a benefit as they should run on any modern computer. Both games are also available separately for £2.69.
**Note, whilst the full games are fully compatible with modern versions of Windows, the demo (also available from Steam) has not been updated and may not work on your computer.