I think the ugliest aircraft would probably be the Junkes G38. There is an observation compartment in the wings and only 2 were ever built.
http://members.fortunecity.com/phreke/cs/junkersg38.html
Unusual perhaps but ugly? - I don't think so. One of these giants was a regular visitor to Croydon Airport before WWII. http://www.youtube.com/watch?v=FP6Qvvdb1io