Unusual loads rather than bikes:
A couple of days ago, I saw that overtaking cars were giving a reasonable space to a cyclist they were passing. When I got to see what was happening, I realised that it was a Fire Officer on his commute, carrying what appeared to be a large holdall-style toolbag with a solid base slung across his back. At the bottom right hand end of this bag hung a bright yellow helmet.
Last night, riding across Figges Marsh, I had difficulty passing a woman cyclist who had a small bookshelf slung sideways across her rack, rather wider than her bars.
This morning, I saw a rider on a disguised Spesh MTB, carrying an unusual load vertically in a rear pannier. I've seen him a couple of times, and the load, while looking quite heavy, didn't stop him riding at a decent pace.
We stopped alongside near Kennington, so I disturbed the 'no talking' etiquette (fortunately he didn't mind) as curiosity overcame me.
It's a trombone, and he rides up to town regularly (for rehearsals? teaching? not sure).