This is a game for an Algebra I class, set up to play with three teams: f, g, and h. The goal: destroy as many points as you can by giving the equation for a line that hits the most (double word score if your line has nonzero slope, perhaps). The inspiration for this is Dan Meyer's "Hit 'em" http://blog.mrmeyer.com/?p=703.
Here's how it works:
Stage 1: Click "New field?" to generate a new pattern of dots. Solicit an equation from each team when time is called.
Stage 2: Reveal functions.
Stage 3: Scores (number of points hit) are displayed for each line.
Stage 4: A line with the maximum score is shown.
Click "New field?" to repeat.
Enjoy!

Use the "settings" menu to change the number of points (approximate, because duplicates are discarded), change the size of the coordinate plane shown, or allow lines that are not functions.
The 'zoom in' function of your browser can be used to optimize the size of the game on the projector screen in your classroom. For different widths, open the webpage in GeoGebra and change the aspect ratio in the "settings" menu. This should get the input boxes out of the way of the points, for instance.
My other applets are available at http://ramsites.net/~cieplowskitj.