PC games, I've not play much stuff in the last few years as I've mostly been a console gamer. But for 'different' stuff I do have some on Steam and love. (I'll even be a sweetheart and post YouTube links) PC games I tend to play are indie titles.
VVVVVV
Really retro graphics, but it really gives it its charm. The soundtrack is pretty awesome. What's different about it? It really only has one game play mechanic, you just reverse gravity. It's very addictive, pretty difficult, it's a real challenge. The video makes it look easy because he's getting it right. Each 'area' is different and offer different challenges, so it doesn't actually feel samey.
Whilst there's no limit on how many times you die (except on no-death mode) but your high score is pretty much, "can I die fewer times this time round?" I think I had something like 2,000 deaths. It's beautifully (and frustratingly) cruel, I've not played anything like it before. Loved every moment of it. It's a cool game.
Limbo
Another game with cruel gameplay. I think the video does a good job of explaining the game. It certainly has some good challenges with trying to find your way past certain traps. I'd say it's a bit different from other platformers out there.
Dungeon Defenders
You might watch the video and think, WTF WoW? How can you get any less unique than that? Whilst this game can be played single player, but is actually based played multiplayers. It is basically a take on tower defence and can be incredibly fun. Combat is all real time, but you've got to plot out your towers as you would in a tower defence game and you've got various waves of things to challenge you. Even interesting boss fights. I play a Monk, so most of the time I'm at the frontline in battle whilst my wizard friend is building the defences. It takes some trial and error too, but definitely a decent indie title.
Jamestown
Okay, it's a bog standard shmup, but still, lots of fun to play, I mean the story is basically American colonisation...but on Mars - I think that itself should be a selling point.
My next one was gonna be Audiosurf, because it is a great game, but instead, I'm gonna give you
Beat Hazard (Warning: May cause seizures). It's an asteroids like shooter, but the levels are based entirely on the music you've selected (so you choose your own music). It has its edge with the music you feed it. It's a similar concept to Audiosurf, but takes a different route. Also, you sometimes get bosses.
But then, you can have
Audiosurf anyway (who said there had to be a limit?)