If it has to be LV only, then my Trevi PM. Beautiful, ladylike, spacious, robust, gets a lot of compliments, and still makes my heart sing after nearly 10 years ♥
If it can be any brand, then probably Hermes Trim II in Rouge H courcheval GHW.
I don't know if I can live in a world if this is a choice I have to make. If it's an LV bag then my Speedy 35 DE print. If it's out of any bag of all time then the Hermes constance or Chanel M/L flap.
One bag for my entire life sounds like a NIGHTMARE!! But if I have to choose one it would definitely be my DE speedy b 35. Holds alot, lighter than most, can be used 3 different ways and weatherproof. The whole thought makes me queasy-1 bag?!?
DE Neverfull PM. Lightweight & (so far) indestructible. Small enough not to be a nuisance in crowded spaces but roomy enough to hold everything I need.