Hellman's Mayo!!! Now, I know what you're all thinking -- they sell Hellman's in the UK. It has the identical label and everything, but it just tastes wrong. So I brought a jar from home one trip and put them side by side. Sure enough, the Brit version had vinegar listed as the first ingredient; the American version had eggs as the first ingredient. And that's exactly the difference in taste -- the US version is fluffy and white and eggy, UK version is thin and sour and beige. Feh.
I've made mayo from scratch in moments of quiet desperation, but it keeps for about ten minutes.
Now that I know I'll be moving, I've started re-acquainting myself with friends I have neglected, mostly in the hopes I can hit them up for favors like the occasional pouch of tuna and jar of mayo. I'm such a weasel.