BitTyrant is a modification for Azureus that, unlike other clients, selects only the peers to connect with that will return the greatest download/upload rate, this has made downloads up to 70% faster than with a regular client.
There is, however, a lot of controversy with this client. Many people believe that it will hurt overall download speed and bittorrent as a whole by only connecting to selected peers, which would leave others in the dust. Though I’d say there’s no harm done as long as you do a bit more seeding than usual. That said, it’s probably best you only use it for painfully slow torrents. Read through the links, FAQ, and papers they provide to decide whether it’s right for you.
Back Door Life 
Just googled here and decided to check it out…. The speed increase is actually very big for slower torrents.
I would recommend this great little app.
Saved me a few hours downloading an old Linux distro!