We start the countdown with the faintest and smallest cluster on our list, M35 in Gemini. At mag. +5.2 it appears to the naked eye as a somewhat misty patch of light. Surprisingly it wasn't discovered until 1745-46. When seen through binoculars M35 is a fantastic sight with the brightest dozen or so stars resolvable. Enhancing the view is a hazy glow surrounding the stars. Telescopes reveal many more stars but the glow effect disappears. M35 is 2,800 light years distant and spans 28 arc minutes which is similar to the full Moon diameter. It's estimated to contain up to 200 stars.
Located about 15 arc minutes southwest of M35 is open cluster NGC 2158, which at mag. +8.6 is faintly visible with binoculars.