Play some Shank 2 with your best buddy when he's on PC. :D

gameglobe ;p or install path of exile or star wars the old republic or wait for tera

CHIVALRY MEDIEVAL WARFARE!

TF2, because...it's fun.

Dustforce.

Its a nice 2D platformer with an awesome soundtrack. If you're into getting high scores you should give it a shot. Not only do you get rated for finishing the level fast, but also for the amount of dust you cleaned on the level.

Cave Story+, it literally was the turning point of indie games and is one of the best indie platformers of all time on the pc

You should try OFfspring Fling. best game evah

skyrim, because its super inmersive, lotsa fun, good difficulty, variety of enemies, interesting and original quest, and has infinite quest :D

I see you don't have any play time on Bad Rats yet...

Play PathofExile , it's free, it's great, it's fun and a great skill system so might check that out, and can also do it with your friends. Ye i know it's just beta but still a great diablo kinda copy, it's a must try.

Nights into dreams. Looks like a beatiful game, old style to it, probably unlike many of the current offerings.
Offspring fling is pretty addictive, but I consider it a very casual game, the kind of thing I only play when I'm stuck on my wife's laptop.

Dungeon defenders is always fun to kill time

skyrimz ?

I would suggest something, but you are shooting down most of the ideas on a very limited list that you have.

play cs. why? it's reaction, it's team tactics, it's thinking, it's cybersport :)

Symphony, if you are so bored, listen to some music while playing the shiny colorful shooter.

Or maybe dungeons of dredmor, easy to kill time with it.

dungeon defenders,because is so much fun imo..better with friends,as every coop games

well legend of grimrock is one of the best games i've played in a long time. great level design, graphics, gameplay... the puzzles are really well thought out. it makes you feel smart when you figure something out or find a secret place. the story keeps you on edge by staying vague until the end and makes a really great atmosphere. falling down pits doesn't kill you, only takes you down one floor. buuuut, my favorite thing about it is how scary it can be. enemies can come outta nowhere and if you aren't prepared then you'll die. 10/10 for me but definitely not for everyone.

Out of all the ones I've played on that list, I would most definitely suggest Dungeons of Dredmor. Very addictive and engaging gameplay as well as a good sense of humor and it gives you quite the urge to want to do better and go further every time you die.

And I wanted to suggest Aquaria :( It is such a great game.

But I'll instead suggestion Legend of Grimrock. My GOTY last year (together with Crusader Kings 2). It is just that good.

Dungeons of Dredmor. Why? Because of Diggles. ^^

Buy Arma II: Combined Ops, install DayZ, and never need another game again.

they bleed pixels... because well they bleed pixels :P

wow your games list looks kind of like mine lets see here
The Binding of Isaac - pull up cheatengine and give yourself a few items and see how the run turns out or do some unique/difficult challenge runs
Bioshock - One of the best singleplayer story games i've played, although hacking and switching from plasmids to guns are a pain, other than that, great game.