Collapsible Industar-22, hands down. Makes the camera truly pocketable, produces surprisingly good photos, has excellent handling and looks smashing too.
Somehow, the J-8 never did it for me. Sure, the photos left little to be desired, but the ergonomics of that lens are simply horrible. It's big, it's clunky, it's ugly, it's difficult to focus (incredibly long focus through, and nothing to grab onto while focusing), and the aperture setting can change at the lightest brush of your sleeve.
The J-12 is my runner-up to the I-22. Once again, it makes the camera more or less pocketable; it has less distortion than any other wide angle lens I've seen; it produces excellent photos (though the flare problem makes the lens absolutely unusable in any form of backlight, since the light completely spills over and ruins the entire negative) and it handles moderately well.