Want to learn some new ones. My favorite is electric man 2 and the world's hardest game. (Finished level impossible)
Pandemic 2 is a favorite of mine, although it's almost impossible to win on realistic because of madagascar!
The Sonny games are probably the best flash games out there. Perfect RPG in flash form. One of the few that I've actually beaten. The Last Stand 2 is also really good, the first one isn't as good. The second one has alot more depth to it. More Zombies is also a load of fun if you want to beat the crap out of zombies and earn some huge weapons in the meantime.
Actually, now that I've been getting into a few more I'll list some more. Karoshi Suicide Salaryman and Super Karoshi Warfare 1917/Warfare 1944 Vending Machine Champ (Alot of people don't seem to like it. Idk why...) Colony Canabalt Palisade Guardian/Palisade Guardian 2: Modern Combat Crush the Castle Portal Flash Version Endless Zombie Rampage I'm sure there's more but those are the ones I really like other than the Sonny and Last Stand games. EDIT: Also, I just remembered that there are ports of actual games to flash. Here's a short list: Doom (Shareware).\ ...........................\ Heretic (Shareware) > All are in one game called "Doom Triple Pack". Google it. .........................../ Hexen (Shareware)/ Alien Hominid. It's an official port by the team who made it to Newgrounds. It's a full conversion as far as I can tell so far, it's just really, really hard.
Pandemic is great cuz it actually runs on the computers in my programming class. Canabalt doesn't cuz they don't have flash 10 but they are reimaging the computers so we'll see what happens
http://www.elementsthegame.com/elementnew.swf by far (was addicted to this for last 2 weeks or so but since have recovered). That Warfare 1917 is pretty decent too.