Magic Pen: http://www.bubblebox.com/play/puzzle/975.htm
Castle Wars: http://www.kongregate.com/games/m0rkeulv/castlewars
Fantastic Contraption: http://fantasticcontraption.com/
Desktop Tower Defense: http://www.kongregate.com/games/preecep/desktop-tower-defense-1-5
Onslaught: http://www.kongregate.com/games/gaby/onslaught2

Perfect Balance: http://www.gamesloth.com/games/Perfect_Balance
I Love Traffic: http://armorgames.com/play/3515/i-love-traffic
Gravity Pods: http://www.wickedpissahgames.com/games/gravitypods/GravityPods.html
The Last Stand: http://armorgames.com/play/269/the-last-stand
Fantastic Contraption: http://fantasticcontraption.com/
Scriball: http://www.gamesloth.com/games/Scriball
Monster's Den: http://www.kongregate.com/games/garin/monsters-den-book-of-dread

Meat Boy: http://www.kongregate.com/games/Edmund/meat-boy
Chronotron: http://www.kongregate.com/games/Scarybug/chronotron
Portal: http://www.kongregate.com/games/Dragy/portal-the-flash-version
Super Stacker 2: http://www.kongregate.com/games/TheGameHomepage/super-stacker-2

Let's be honest, Ganguro Girl Deluxe is what you're really looking for.

But yeah, on a more serious (but extremely addictive) note there's my all-time favorite Winter Bells (because I am a bunny-person, after all) Great game, which is worth playing if only for the experience it gives you just before the first time you lose at it. Seriously.

Wow, Sarzy, that Chronotron gets pretty tough. Trying to think of everything I have to do before I do it. Awesome concept for a puzzle game.

>> ^Sarzy

I've been playing superstacker all week. It's awesome. I'll have to think about my list for a bit.

Gemcraft: http://armorgames.com/play/1716/gemcraft
Sonny: http://armorgames.com/play/505/sonny
Mud and Blood 2: http://www.kongregate.com/games/urbz/mud-and-blood-2
Dolphin Olympics 2: http://www.kongregate.com/games/arawkins/dolphin-olympics-2
Monsters Den: Book of Dread: http://www.kongregate.com/games/garin/monsters-den-book-of-dread

I have a bunch of others but those are ones I can't get enough of.

Any classic, top-down RPGs out there?

I don´t have a favorite but this one is always fun to play.

Achievement Unlocked: http://armorgames.com/play/2893/achievement-unlocked

^ ^
That's frikkin' awesome

The Shift series is my definitive favourite:

http://armorgames.com/play/751/shift
http://armorgames.com/play/964/shift-2
http://armorgames.com/play/1846/shift-3

try this: http://www.gamedesign.jp/flash/chatnoir/chatnoir.html

Newgrounds.com Check it out.

Minions: http://www.casualcollective.com/#games/Minions

Portal: http://portal.wecreatestuff.com/portal.php

The Space Game: http://www.casualcollective.com/#games/The_Space_Game

(and many great games already listed)

Don't forget an old classic, the dark room http://dark.room.fizzlebot.com/

this was fun too http://www.kongregate.com/games/BerzerkStudio/heros-arms

http://www.kongregate.com/games/Mazapan/you-have-to-burn-the-rope

This one is like portal, in no way other than that it is short and has an awesome end credits song!

^ That IS awesome!

*quality games

Awarding Ryjkyj with one star point for this contribution to Sift Talk - declared quality by dystopianfuturetoday.