I use WS_FTP LE. The one that I use is an old version. Must have been been made for Win98

But it is free, is light on resources and does its job perfectly fine. Of course, it doesn't look as nice as other "modern" FTP clients. But the interface is neat. I also have a 2007 version of WS_FTP. But I still use the old one. If anyone wants this older version, I can give it. It is freeware.
I have tried SmartFTP and it sucks! I've used it just once. I transfered a folder. It skipped some files and didn't even give any error/warning.