I'm surprised I don't see many topics about great Flash games. Maybe that's because I'm a Newgrounds whore and you guys aren't, but whatever. Let's share our favorite flash games~!

XENO TACTIC is an amazing Defense game. Yes, it is better than any popular Defend Your _____ game involving stupid stick figures. This game gives you a field, occasionally with some obstacles, and six turret types to place where you wish. Turrets can be upgraded, but that costs money and time- which is precious in XENO TACTIC. You only get resting periods if you manage to herd aliens into a death trap and finish that wave off before the next one comes in 2 seconds later.
XENO TACTIC is very hard, looks great, sounds great and has unlimited strategies.
http://www.newgrounds.com/portal/view/382321

Evil Nights has a terrible name and can lag somewhat. It's a strange RPG/Defense hybrid where you can turn your wizard into a vampiric, teleporting fiend; a hardy mage that simply won't die; a cleric that relies on crossbowmen for defense and spends time running around healing buildings and people; a mage fond of slinging thunder and lightning constantly with no regard for the town and so many other possibilites. Again, it can lag a bit (especially if you teleport into a large clump of demons), but it nicely balances the strategy of an RPG and the difficulty of a platformer. Indeed, this may be the only RPGish game where jumping does you any good.
http://www.newgrounds.com/portal/view/385178

-Red-. Holy shit. It's a space invaders game with creepy music, simple graphics (but anti-aliased!) and some awesome physics. The aim of the game [sic] is to push meteors off of the screen by hitting them with little balls and big balls. You have little ammo and it  replenishes slowly. Extra bases can be tricky to defend. It has gigantic boss meteors that take up the entire screen. Sooooooooooooo cooooooool.
http://www.newgrounds.com/portal/view/341598

Sinjid: SotW on the top of your browser window means that you're playing a pretty cool RPG with lots of customization. Plus, you're a ninja. There's not really much else to say... it's a turn-based RPG with customization. And ninjas. Okay?!?!?
http://www.newgrounds.com/portal/view/209736

Not a game, but one of my favourite Flash thingies.

http://www.newgrounds.com/portal/view/193426

Not a game, but one of my favourite Flash thingies.

http://www.newgrounds.com/portal/view/193426

I was just going to link this. Spastic!

Not a game, but one of my favourite Flash thingies.

Wow, that was really great. 

I am one of the only people in the world who has ever heard of or played this gem: http://www.shape9.nl/games/showcase.html

I'm still just barely in the top 7, with a score I set a few years ago.

wow red is sweet! i went 578 seconds.

I got to question like 60 on the first impossible quiz then gave up. I can only restart so many times a night. What's the answer to the one with the picture of the duck?

I was just going to link this. Spastic!

You just aren't fast enough, blondie!

http://portal.wecreatestuff.com/

The flash version of Portal. Fun for all ages.

So, you like Tower Defense type games, huh?

Flash Circle TD
Desktop Tower Defense
Vector TD
Bloons Tower Defense
Bloons Tower Defense 2

If anyone knows of other tower defence games, link me up!

@warpped: Ay go' mo' po'co', fo' (For those who aren't Eliza Doolittle or a gangsta, that is the slang for "I have a higher post count, you silly boy).

@DarkPriest: Yesssssssssss. Thanks for those links~

I have faves and here they are:
http://www.newgrounds.com/portal/view/276616 this is pretty catchy tune
http://www.newgrounds.com/portal/view/252756 pure awesomeness cos its doom
http://www.newgrounds.com/portal/view/382208 really really fun, a physics like defend your base type game
http://www.newgrounds.com/collection/supermariobrosz.html and this as its one of the best Flash series for a crossover i've seen so far

Ownage Burst - Very addictive shoot 'em up. Loads of fun. Only a demo though...