My all time favorite is the Ibex Woolies 1- sad that they're no longer in business.
My Icebreaker 200g merino top is also okay, as is my Woolx 160g top. The Icebreaker gets a bit of use when it's a bit cooler, but not cool enough for multiple layers of wool. It also gets a bit more use with a mid-layer when it gets very cold, like 0F.
My "mid-layers" for cold weather consist of various merino sweaters that have started to get holes or stains or are otherwise out of the work wear rotation.