I've tried most everything but I only like (and use) these four (all for Windows):

utorrent, version 2.2
Deluge portable
Transmission portable
Tixati portable

I also tried qBittorrent and it totally froze my computer a couple of times, so I don't go near it anymore...
I don't like Vuze/Azureus either as it downloaded automatically something I didn't ask for!
BitComet totally spies on you so better stay away from it!
I also tried some others, not even worth mentioning...