Which aircraft have made notable use of lateral asymmetry?
There are quite a few asymmetric aircraft, most of which are,


experimental
engine test beds 


A good example of experimental aircraft is the NASA F-16XL



F-16XL with supersonic laminar flow control experiment (black area on left wing, front) or "glove." Image from nasa.gov

Aircraft used as engine test beds are usually asymmetric. The following image shows a B-47 Stratojet used as engine test bed for the the Orenda engine earmarked for Avro Arrow program.



Image from silverhawkauthor.com

A closeup of the rear:



Image from google

English Electric Canberra PR9s had offset canopies.



By MilborneOne - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13266605

So did the de Havilland Sea Vixens.



By Yeovilton_Vixen_2009-001.tif: Nigel Ishderivative work: Cobatfor - This file was derived from &nbsp;Yeovilton Vixen 2009-001.tif:&nbsp;, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19477903

Of course, all 'conventional' helicopters (with tail rotors on one side) are asymmetric, but I don't think that's what you're after here.

Also, see this page and the Wikipedia page on asymmetric aircraft. As a disclaimer, I wouldn't call any of these aircraft 'ugly'.