I use three different ones
Filezilla
Winscp
WS_FTP pro
I have different servers I use and some require Winscp because of the type of security they have, I use WS_FTP Pro at work and Filezilla at home
I use transmit and coda on my mac and SFTPDrive on Windows. I tried the mac version of SFTPdrive and it wasn't as good as panic products so far, but I have hope.