Ballistic Overkill is a fun and cheap FPS that I've put many hours into, it's now free to try for a few days and on sale with 50% off if you decide to keep it. The game has been out for a year now (minus a little time for the Linux build), so they're celebrating.
The developer just put out a fresh update today as well which adds in female skins for the Wraith and Tank classes. They say they're working to add more female skins in a future update too. On top of that, they've also added in 238 new weapon skins, allowed you to equip multiple accessories at the same time and previous seasons crates (their form of free loot boxes) are now permanent drops.
I'm hoping they have some bigger updates planned, as it's a very fun game but it sorely needs a few new maps.
Find Ballistic Overkill on Steam, you've got nothing to lose if you try it out.