Created by Jeff Weber and lead by Ian Qvist, the Farseer Physics Engine (now changed to Velcro Physics) is an open source high performance 2D collision detection system with realistic physics responses. It was originally based off the XNA port of Box2D. This download includes source code, samples and documentation. It also includes the source to Velcro Physics. Check out the samples inside the Projects folder. The Simple Samples projects were created by Mads Laumann. The TestBed project was ported by Marcel Härte to MonoGame 3.6. Also, check out the Black Hole Gunner game located in the projects folder. Black Hole Gunner was a game created by Libor Vilimek, Jan Švehla, and Vojtěch Ruschka. The game was made at the end of year 2010 at Czech Technical University (ČVUT) in school subject "Computer games and Animations". The game is based on the Farseer Engine, built in XNA 4.0, Visual Studio. Black Hole Gunner was made within 2-5 months with no game-experience creation.
Farseer has a ton of features!