Internet Explorer and Firefox Compatible Games:

 
Lights Off - The object is to turn off all the lights.
Jirbo - Match the farm animals.
Duck Hunt - Nintendo Classic shooting game.
TicTacTouch - Tick Tack Toe!

Firefox Only Compatible Games:

Castle Feud - Aim, adjust the power, calculate the wind and fire at will!
Battlefleet - An awesome iPhone version of the classic board game Battleship.
Bejeweled - Yeah, one of those games like Tetris only not.
Ninja Ropes - Just start clicking you'll get the hang of it!  A lot of fun!
About Sunset - Fun 3D Game with spiders in it.