For your Information Top ten actions games online  can be as follows but its according to my taste as a teen i love to play all these games online but I am sure you will also like these games.
Super Mario Bros 3 - Which is also known as also referred to as Super Mario 3 and SMB3  super Mario Bros 3 is a video game developed by Nintendo for the Nintendo Entertainment System , Super mario bros 3 is the 5th online video game in the Super Mario series
Icy Tower  is a great way to pass some time falls under Arcade Games teritory, In Icy tower game  the goal of a player is very simple but tricky help them to reach the top and complete the task without falling or failing
Halo Combat Evolved  falls under the game characters of First-Person Shooter Games,  The Halo series featuring  science fiction and lots of action game having Ancient structures and different alien races series,Moreover  Halo is a created by Bungie and developed by Microsoft Game for microsoft Xbox 360, Halo 3 is the popular games for Xbox360.
Cross Fire is a also available  free online under the category of  first-person shooter cross fire has many games modes and level , from the starting till the end you will not loose interest in the game
Call of Duty 4 Modern Warfare is a also a first-person shooter video game player can play the game online this game is specially designed for Nintendo Wii , Xbox 360, PlayStation 3 the game is in great demand and fall under the search og great demand games in 2010
Modern Warfare 2  turn based strategic war gamefalls uner the category of first-Person Shooter Games in 2010 the game is gaining excelent popularity since the game is easy to play but ver action oriented and interesting.
War Rock  is a Freely available online to play the game War rock is a 2 player games fall under the category of Online multiplayer games the game is having latest tactics a first person shooter game a very good war , Main Battle Tanks, and Helicopter Gun games , aeroships wars
Little Fighter a very popular fighting game seems to have great  punches in the game as well as rocking kicks. the game Little fighter is very well popular among young kids as well as teens, the game always fall under the top ten most wanted action games by kids in 2010
Rumble Fighter another astonishing action game also can be considered as  Fighting Games great demand by adults the game is also available online to play for free offered by many websites.
Return to Castle Wolfensteinis a first person shooting game within the  Enemy Territory game is very accepted by players of all age group the game can be find out with the help of google search online.