Open Sonic
If you are a big Sonic the Hedgehog fan and enjoy the many titles that was released under Sega back in the day; you'll be glad to know that now there's a free version that you can download and play. Open Sonic is a free Sonic game that reflects the original style of gameplay (along with some modern twists).
The game is released by opensnc.sourceforge.net. The cool thing about this game is that it contains almost everything that you've come to love from playing this blue hedgehog. The graphics are great and you carry almost every skill that Sonic and his friends have.
Enjoy this awesome open source version of Sonic and his friends. You'll definitely have a grand time getting in touch with your inner kid.