rTorrent is a popular command line based bittorrent client. It provides very powerful features yet it is very light on the system – contrary to other bittorrent clients like Vuze. More here
In the previous howto patches for magnet link support were provided. With the current revision 1169 magnet link support has already been integrated. However some of the inner workings were changed and the colour patch was modified to work in the current revision.