CivilizationVComplete - 92% off, $12.27
http://store.steampowered.com/bundle/575/Sid_Meiers_Civilization_V_Complete/
Battle Brothers is on sale; as of patch 1.1 devs have said they are done with it (and basically no mod support, sadly), but you can generate random seeds for each game for some replayability.
Basically, your mercenary company has been all but wiped out, and you and 3 others are the only survivors. you have to struggle to rebuild while traveling for contracts from town to town, trying to get poor farmers and fisherman and various other backgrounds into a team that can actually fight decently well. There is also a minimal trade system involved, as you can buy trade goods at towns that produce them and then turn around and sell them in other places for profit.
Combat is turn-based, and there is enough variety in weapons to make each type useful and interesting (swords against lightly armored targets; flails are capable of just ignoring shields, axes can smash shields to bits, etc). Worth checking out.
Sucks shit.
Have you considered moving to Hungary, so that your nation shape will mirror your computer's capabilities? :p
My recommendations:
Kingdom: Classic - -70% (4,49€)
1-Button sidescroller strategy, where at daylight you build up your kingdom by (literally) throwing money at problems, and at night huddle behind the barricades to await the nightly onslaught of the Greedlings from the dark woods beyond the wall. I got it because I liked the original version at Newgrounds, and the upgraded Steam version has been a great boon for graphics, sound, gameplay and depth.
Rebuild 3: Gangs of Deadville - -40% (7,19€ / 12,59€)
Zombie-Apocalypse-4XS.
If you loved the original two Rebuild flash games, you are bound to like the 3rd installment on Steam too.
As a purist who prefers the simple Rebuild 1 I find the micromanagement and details a bit much mechanically, but such additions as other human factions you can interact diplomatically with or actual plot-lines unrelated to the winning conditions are very welcome.
Steve Jackson's Sorcery! Complete - 40-60% (14,97€)
The legendary Fighting Fantasy CYOA 4-part campaign, in a package that leaves enough intact to keep it recognizable and shakes up enough to make it fresh if you know the original books from the 80s, at a price that during the Steam sale is actually cheaper than the original books. If you know the old books, you know what you get into and buy it blindly. If you don't know them, you are in for a treat that feels very much like playing a pen&paper mini-campaign under a well-prepared GM.
The major weakness is that it was obviously built for mobile first with PC as an afterthought, and the production value (as with the free music cobbled together from online sources) is sometimes low, but as a grognard that didn't bother me compared to the superb writing, story and the world-building.
I will check those out, dunno if it's exactly my style though
You can first sample the Newgrounds versions of Kingdom and Rebuild 1/2 for free before you decide to spend money on them.
You already know some of the old FF books of Stave Jackson and Ian Livingstone IIRC, so with Sorcery! you should have a rough idea what you get into.
Battlezone 98 Redux - £3.74. Great FPS / Strategy game. I've played it again and again.
It's been rebooted into one of the flagship VR games.
Also +1 for Darwinia.
Prices are in britbong dollars, sorry.
Old and oldish games, or well known ones
New or not well known
EDIT: Running With Rifles - £4.40, top down shooter with hundreds of units, fun as shit