The North Face Cirque Top Delta 1/4 Zip

This is one of the best base layers out there. I have been using this for the last five years. More like abusing it. It is still going strong after more than 150 washes (at least). I have used it for hiking, camping and most importantly for geological fieldwork in all conditions - from cool fall days to raging winter blizzards (of course you have to layer it with fleece and shell in the blizzard). It's perfect for any outdoor activity. Worth every penny!!!