The best threadless stems on my vintage rides are at the very least context dependent (aka with modern go-fast components and wheels usually), but my steadfast setup with them is right off the/on top of the headset to give it that threadless look. Round cross-section, in black, helps reduce the mass. I picked up a Velo Orange unit with an octagonal cross-section (more like a square with heavily chamfered corners that are nicely radiused). Polished. The chamfers really cut the mass out of the stem, especially as the polished nature grabs so much light. 26.0mm clamp keeps the handlebar end of things looking reasonable.