Here are a few of my favorite flash games out there… a bit outdated, I will go over them again soon.
Pixeltruss
This is where I do my collaboration with Simon. Read more about our games (including Ripple Dot Zero) here.
Mirrors Edge 2D
The official flash game for Mirrors Edge! This game is probably the best flash game I have ever played yet! It even beats the crap out of the real game – by far! (Only its a bit short).
Kudos to Brad Bourne! Well done!
Desktop Tower Defence
This game is one of the most addictive flash games I have ever played! And I still cannot stop.
Place cannons at strategic spots and try to hold out as long as possible!
The Terrific Menace Of The Invaders From AudioGalaxy
An extremely well made point-and-click adventure game similar to the old classics like “Day Of The Tentacle”, and “Full Throttle”. A really great game so give it a shot!
Gamma Bros
This game is wonderful! The pixel-art! The controls! The music and soundeffects! The bosses! Enough said: Play it now!!
Kudos to the Pixel Jam team!
Helicopter game
I have played this game way to much. Think my top score is somwhere above 3.000.
It has some flaws but is simple… and really addictive!
Bounce Out
This is a puzzlegame (made in director and not flash), and it has some really annoying commercials before it starts… but fun as hell!
Globulos
Flash multiplayer game. A few levels are free to play. Try it out against a friend!
FLOW
This game is just… different. Cannot be explained. Can you reach the bottom?
N
Great physics in this flashgame where you are a ninja that collects gold and just trying to survive… not an easy task.
An extremley welldone and fun game. The downside is that you have to download it to be able to play (but it’s surely worth it!)
Gyro World
This is a very old game that I played a lot a couple of years back… although the controls and hitdetection aren’t very good it is a huge world to discover! And quite fun until you die too much…
Fighting game by Smooth Operator
Almost as good as Street Fighter II 
By my co-worker “Smooth Operator” (he is really a .NET-programmer)