"I'm with the Pilots" by Ladytron. Not so much that it's especially short, more that it's an otherwise good and atmospheric song that finishes in an unsatisfying way what sounds like two thirds of the way through.

(It sounds like it's following the usual pop-song structure, but ends abruptly after the middle eight without a final chorus or verse/chorus).

I think that a few of the short songs mentioned are appealing because they're so short. I like that quirkiness in some songs. I can't think of any that I wish would be longer.

Napalm Death - "You Suffer" one secons long.

Tea for the Tillerman –Cat Stevens.

The only one of his I like and it's 1:01.

Another one I've just thought of - All The Small Things by Blink 182. It's only 2:51. I challenge anyone to listen to that song and not feel in a happy mood after doing so