For a baselayer I like Icebreaker shortsleeve tee's and Smartwool longsleeve 1/4 zip shirts. This stuff is so comfortable, quite durable as well as warm and fresh smelling between washings. If you spend the entire winter in the bush of Northern BC and Alberta working around high pressure gas wells, as I do, you will not only be warm, but confident that it wont melt to your skin underneath your Nomex if something blows up. You'd also be surprised how comfortable a merino wool t-shirt can be in the Summer when it's +80F.
