It's not clear what you want to do, so let me assume that you want the local files to be owned by user A and the remote files to be owned by user B. If you run the following command as user A:
rsync [options] B@remote.system:/path/to/remote/dir /path/to/local/dir
this would have the effect you want. But it's not really an rsync issue (so I'm not elaborating on what the above command will do, I'm focusing on your question); even with your graphical SSH client you should be able to do the same if you run it as user A and set it to log on to the remote system as user B.