if only one...
if one ask me, if you had to bring with you just one top garment for a week trip in temperate environment, it would be this one in black or grey. I love it, light, warm enough to let you feeling good/OK at a wide range of temperatures (40 to 70), odor free... You can wear it as a piece of underwear, or as a light LS tee, alone, or under a jacket. The only downside is the fabric, so light that it's really fragile. Try to handwash it as much as possible and you'll enjoy it for a long time