Do you like retro games? Check out Pica-Pic and you can enjoy playing oldschool handheld games like the Game & Watch. It might not give you the real feel of the handheld games from decades ago but it lets you enjoy some of the classic handheld games in all their monochromatic goodness (or badness) in the convenience of your browser.
The controls for each game are mapped to your computer keyboard. Don’t worry about the “how to play” instructions, they’re pretty easy to figure out. Simply remember the keyboard keys that are assigned for each button and you’re all set to go.
You need to have a flash player installed in order to play the games. This means that you can’t play the games on your iPad. I’m not sure about Android tablets though. But, mapping the controls to keyboard keys only will make it hard to play on other tablets that supports flash.