In the UK I wear a size 15UK but in the USA I take a 16EE shoe (measured in Nike store, ECCO, North Las Vegas in Aug 2010).
I actually have a 15.5 left foot and 15 right foot (UK sizes) but most size 15UK/50EU shoes fit OK with the left feeling a little tight.
When I get to the US it's great as I can visit a regular sneaker shop and get really comfy shoes, where here in the UK I have to visit specialist BigMan stores or order online and return those that don't fit.
Hardest was always motorcycle boots, but recently the manufacturers seem to be waking up to people with big feet.
My last pair were Alpinestars Andes (good) and current pair are Held Annone (excellent but SNUG!).
I cannot wear thick socks with any of my footwear.
I met someone years ago with size 21 feet. Made mine look like kids feet <LOL>.
He was 7'2" and had HUGE hands. He was a basketball coach and ex-basketball player.
Hahaha... I went to a site for police supply, Galls.com. They have cop boots that go way up in sizes (I guess that is why they used to be called flatfoots) and are pretty cheap (under $100 USD). Anyway, most comfortable boots ever, and so far, indestructible. After trying one pair, I bought 2 more pair (one backup and one taller ankle size). My Milwaukee brand boots were more expensive, wore out completely (hole in bottom), and the zipper broke after a year.
Yes, I can usually find sneakers, but everything else end at size 13. Forget about off-the-shelf clothing.