Okay, so I haven't actually played all of these, but they all have excellent reviews, which counts for something.

Star Wars Jedi Knight: Jedi Academy
Star Wars Jedi Knight 2: Jedi Outcast

These two older games are $3.50 each and, I'm told, feature the best lightsaber combat of any Star Wars game. It also has first-person shooter elements and (of course) Force abilities.

Arma 3: Hardcore military simulator, with heavy emphasis on group tactics. Currently $13.59 for the base game or $23.79 for the Apex Edition (which includes a bunch of DLC). You're going to need a clan if you want to play seriously, but luckily there's a web page where you can search for open ones. I'd only buy this game on sale because of how serious a commitment it is; a single mission can take an hour or more from briefing and role assignment to completion.

The Witcher 3: Wild Hunt
Excellent dark fantasy RPG, currently $20. I haven't played much of it (sadly), but what I've played is absolutely perfect. Right now, the GOTY edition is the same price as the base game; effectively, all the DLC is free. Just make sure your computer is beefy enough to run it.

Some things I can suggest:

-Mount and Blade: Warband: Okay, if you're here, you'll probably like Warband. It's a medieval RPG/Combat sim, and you can command armies and order around soldiers, and there's also a multiplayer mode that supports over 100+ man matches, and... what else do you want?

Maybe an active modding community, an expansion/new game/DLC thing where you play as a viking in a game version of RL Scandanavia, another expansion where you can fight in multiplayer set in the French Revolution? Because it has all that too.

-Civilization: It really doesn't matter which. Just... one of them. Do I even have to explain?

-Dawn of War I and standalone expansions (although Soulstorm is... not the best): Do you like RTS games? Do you like Warhammer 40k? If so, buy these. They're great.

-A game by Zachtronics: Really, any of them, provided you're a programmer. Save for Ironclad Tactics, they are some of the best puzzles for programmers out there.

-Strife, Veteran Edition: Strife is a proper, old-school shooter, built in the Doom engine. But it's also an RPG hybrid with an interconnected word, actual story, and voice acting, where Killing All the Things isn't always the best way to proceed.

-Quake (any of them), and Doom (1, 2, and 4): What can I say? These games are pure, absolute classics, have great campaigns (well, Quake 1 and the Dooms do, at least), great multiplayer (if you can set it up and find anyone online), and are just all-around fun.

-Half-Life: This one's a tad frustrating, but I've been playing through it, and overall, I've been enjoying quite a bit. Grab the sequel, while you're at it.

-Portal (and Portal 2): Go play some of the funniest games ever made. Great puzzles, as well.

-Psychonauts: Portal is funny. This is, too. It's a classic 3rd person platformer, mostly getting by on the writing alone, but there are some great levels here as well: The Milkman conspiracy stuck in my head for well over a decade, long after the name of the game it was attached to had faded.

-To The Moon: More of a visual novel than a game. Do you like crying? this is for you.

-N++: Remember N? did you like N? play this. It's good.

-Bastion, Transistor, and Pyre: Look, just anything Supergiant makes. Their games are gorgeous, play well, and have good stories, and that music and voice acting...

-The Stanley Parable: You probably know it already. It is good.

There is soooo much more. But that's what I'm listing for now.