What is your best ever S&B "investment piece"?

[Callipo]

By which I mean amazing cost per wear and always make you happy when you put it on - does not necessarily have to be very pricey, but I'd like to hear about those too!!
FWIW mine are a Gap down coat which is just brilliant and nearly 6 years old - every time I put it on I think - I wish I'd got two of these! They have never done such a good one since. And a MaxMara black pencil skirt, 12 years old and worn at least once a week.

A chocolate-brown full-length down coat I bought while sheltering from a snowstorm in Saks Fifth Ave - it's flatteringly fitted, with a hyuuuge fur-trimmed hood and makes me feel like Angelina Jolie. The best thing about it is I can't remember exactly how much it cost (sales tax, blizzard panic, exchange rate) but I do know it was about 75% off, and I've worn it every winter. Weirdly, the clothes I buy in emergency conditions always turn out to be long term winners, possibly because when I really need something, I don't argue with myself so much about the price or whether it'll go into the sale - I just get it.

Or my Tiffany gold hoops which I've worn every day since I bought them for my 30th, forsaking all other earrings, now and possibly for ever. Cost per wear, a bargain.

I've also got a lot more than £9.98 wear from my MN scarf