Swords and Soldiers
Foreign Legion: Buckets of Blood
Who's That Flying? (a.k.a. WTF?)
Bob Came In Pieces
and
A.R.E.S. Extinction

Are all fairly short and highly engaging.

Should mention that A.R.E.S. requires a bit of old RPG style spamming and farming but there are only five levels and it's a really fun game.

Also Bob and Swords and Soldiers have extra challenge modes if you want to prolong lasting appeal.

if you like rogue style games, i'd recommend Dungeon Crawl.. unless you're somehow exceptionally lucky, or just way better at it, than anyone i know.. a session won't take long ;)

http://crawl.develz.org/wordpress/downloads

if you havent already done it i'd say Enslaved, i did that in under 8

i'd also agree with all the ones you put forward (just did both Deathspank games recently and have done the others)

If freebies are acceptable, I'd recommend a decent Turrican fangame under the name "T4 Funeral". There's also a Lionheart remake floating about somewhere that's even been endorsed by Thalion (the original developers of the original game).

If it's commercial (i.e. "paid for") games you want that don't come with DRM (at least as far as anything beyond entering a simple license key), I recommend the following quickie shooters:

Jets 'n Guns Gold
PixelShips Retro (There's also the free version, Pixelships)

There's always the Sword of Fargoal remake, too.

Trine

Great little game, a light platformer where you can switch between 3 complementary characters. The game features a physics engine, allowing for some creative solutions to the puzzles. Highly recommended, if only for the cute art direction. The price should be decent (I bought a 10€ box in my usual physical shop).

It's playable by 1, 2 or 3 players on the same computer : just plug in the appropriate number of USB keyboards and mouses. Gamepads are supported too, but the mouse is really recommended when playing the mage (for the warrior, gamepad is OK).

Nyxquest seems alright so far, though I haven't got that far in it yet. Puzzle/platformer type, novel enough to be interesting.

I'll second that. I own the game but have only had time for the demo so far.

Appears to be a rather short platformer yet very enjoyable and original.

On that same note Trine is also very awesome.

Nice suggestions all, I'll be checking some of this out as soon as I get some laundry and dishes going (and drink coffee, because who can function without that?)!

I can't believe no one has mentioned Beat Hazard. It's a perfect game for a quick blast.

Is Icy Tower still around? That *crap* was fun. You could use any one of multiple custom or unlockable characters each with it's own attributes. I think I scored the highest (no pun intended) with the Commander Keen-(from Goodbye Galaxy)-on-pogo stick sprite. I don't think the online (read: submittable) scoreboards/leaderboards are around anymore, but it's still a good "coffee break" game, if you can find it and the developer hasn't let it's site turn into one of those "Download thousands of cheap-ass games for free, but beware of adware!" sites.

Well better than shelling out $50 for something that can literally be beat in 20 minutes (Contra) or Under 3 hours (Monkey Island).... two games might I add are considered two of the best of there respective genres.

How soon we forget the past.

Was Contra really $50? Are we talking about the original? BTW, HardCorps Uprising comes out next week.

I counter your Beat Hazard with my Audiosurf. You went directly into my trap!
How is ProgressQuest a quickie? My current character (a lvl 68 Talking Pony Voodoo Princess called Dreamfluff) has taken months!

Samorost, and the sequel. Beautiful, quirky, and quick indie titles. Got both for $7 a few months back, got about five hours out of the two combined.

Oh, and a little flash game called..uh. Mindscape. It's actually free, and you'll only get about 20-30 minutes out of it, but go play it. Preferably while you're wired from that coffee. That game will mess with you ^_^