Action games
If you don't play games that much, there is a big chance you have played an action game, e.g. a shooter, at some point. This category is full of games that won't let you get bored.
Frontlines: Fuel of War
Intrusion 2
Crazy Shooter Online
Robocraft
Watchmen The End Is Nigh
Vampires vs. Zombies
Assault Droid
Battleborn
Ambulance Rush
Quick Shooter
Skies of War
Sudden Strike II
Subterrain
Far Cry 4
Half Life - Zombie Edition
VEGA Conflict
Dynasty
TimeShift
AlienHallway
True Combat: Elite
Professor Cornelius
Saddam Osama Fly
MicroMan's Crazy Computers
Tom Clancy's Rainbow Six Vegas 2
Tank Hunter SGF
X-Blades
Rocket Shooter
Starcraft Retaliation
Sunset Riders
Discover FDM
Add-on support
You can get add-ons that download files/video from arbitrary websites.