Brawl is a somewhat interesting new homebrew game for the Sega Master System. It mixes various known video games characters such as Alex Kidd and let you fight against other well known franchises. Also it takes backgrounds from Wonderboy and other games and mixes it up, which in sum makes up a nice gaming soup á la Super Smash Bros. The game is still in (slow) development and even Sonic is said to make his appearance in this game. Make sure to keep your eye on this project as it really develops nice.
This is a perfect example of what free, non commercial, fan games can look alike.