^^ Yeaaaahhhhhhhhh~! :-D
There's Republic Commando for PC, which was functional if not stellar. It isn't really grimdark, but there's a lot of blood and guts compared to any other Star Wars game.
Battlefront 2's campaign is about as grimdark as Star Wars gets, but also boring and repetitive. You'll start to hate it after the seventh "gravelly-voiced narration with creepy chanting over blurry FMV" cutscene.
KOTOR II is also pretty adult, and not in the superficial "rah rah war is hell" manner of Republic Commando and Battlefront 2... that is, if you can chug through the mind-numbingly dull first act on Peragus and Telos. Get the Restoration Patch if you do decide to play, it clarifies a lot of story points that were left unfinished.
I've beat that more times than I can count.
No, I loved it. I thought it was awesome seeing it from the clones' perspective, their regrets and motives and such, and how while they were fighting for the Empire, their breed were slowly dying out, and most of their unit weren't even clones anymore. Battlefront 1 didn't even try to tell a story so it was a big step up.
I don't like KOTOR, and I could never get through it because of how boring it is, though I do agree that its a great game. Just not a fan because of the combat. Melee lacks weight and it really bothers me, and whenever I play blasters I get owned. Prolly just suck. My friend is way better at it. :p