There is this small hotel in Las Canitas
http://www.248finisterra.com
There is also Home Hotel in Palermo (my personal favourite)
http://www.homebuenosaires.com/EN/index
and the last time I liked this one
http://www.atemposuites.com/index.php
P.S. This reply has been written by a non native english speaking member,without the use of any translation web page, so any mistakes should be excused.