This was years ago, but since I've just gotten back on the wagon, so to speak, I thought I'd mention it...
For a laugh, and a bit of a challenge, I thought I'd make a two player game. I settled on Pong, because it was simple enough. The left paddle was controlled with two of the letter keys and the right paddle was up and down. One character was a player, but the other was a sprite. By pressing the correct key, it "moved" up, or down.
The "border" of the game was a sprite. Because I couldn't simply make a tile to bounce a sprite off, it had to be this way. For some reason I did it a certain way that each horizontal line at the top and bottom of the screen had to be three sprites, two of equal length and one extra. The ball, when it hit invisible sprites on the left and right of screen would add a score to the correct side. Then it would start from on one of three paths and it had 100% inertia, so it kept going.
Unfortunately, the game was very dull. It didn't move fast and every time you hit it, or it hit something, it bounced at exactly 45-degrees. The reason I didn't post it was because if it hit one of the three wall sections (either on top or bottom) it would shift that section of line out of whack. I never posted it, because I couldn't fix it and didn't want to post an unfinished example, no matter how ambitious two-player was.
I am pretty sure the project has been lost to the ages now.