When you say fastest do you mean Dl speed as this will depend on your ISP Connection Torrent µTorrent is a great little torrent app HTTP Jdownloader download almost everything with this FTP FlashFXP the best FTP client IMO
U forgot to mention so much clients. Azureus, Transmission, and don't mess with http, ftp. Those are diferrent protocols
I use FlashFXP also and I think it's very nice client, however I don't use FTP too much. For synchronizing with usual servers I use Beyond Compare which does all necessary task automatically, Just wunder if Jdownloader is capable of vanquishing the download sites using captchas aka filesonic, fileserve and similar
Taser mentioned Azureus Azureus is now called Vuze, but you still run it by running Azureus.exe etc, lol.
I hate when both BitTorrent and uTorrent update themselves automatically [although i have that option unchecked in the settings window] and the settings are all wiped out. First i was using BitTorrent and then uTorrent but it's all the same. Both get updated automatically [although i have that option unchecked in the settings window] Every time they update themselves i lose all the settings and I have to do it all over again. Hate that.
Vuze was the fastest but since the last update I can't connect to many seeds and get faster dl speeds with utorrent, but I don't use torrents much anymore (my hdd is almost full...)
Interesting to see that nobody is using MediaGet 2 for Torrent's, Movies, Music etc.! I use that Russian Apps and it's working better that uTorrent for me. As FTP I use 3DFTP for some years because it also has an build in Accelerator and Resume function, which is quite important (for me)!