For me, the most surprising thing I've got in this category is a cheap shirt-- short sleeve, plain black button up, 100% "sueded" polyester. George brand, bought at Wal-mart nearly 20 years ago. I don't know how, but it's still showing no signs of wear despite regular use. I'm sure everything else in my wardrobe has turned over at least three or four times since then.

I would likely not buy the same shirt now, just due to changes in my attitude towards clothing consumption, composition, etc. It's surprising though to find examples like this when the message about BIFL items (specifically BIFL clothing) is that they come with a price premium.