Depending on what band I'm on, I use a Kaito active loop antenna. It works quite well for MW and SW DXing, but my little DX-398 has such a tendency to overload that I pull the antenna and just use the built-in whip if I'm going anywhere near LW.
One of these years (and this is true, not just idle daydreaming) I'm going to move to a bigger place, and then there will be a balcony-mounted antenna, landlord permitting. If the mount is light enough to clamp or be magnetized to the rail/floor, I can't see a landlord objecting too strenuously. Now I'm pondering antennae to use in that situation. Hmm.