General Recommendation codes are most common.
rare earth
The transition metals are the most common, and are found in the middle (groups 3-12) of the Periodic Table.
401.9 is one of the most common use codes
F0 is the most common category.
Group III machines
The most common type is main-sequence stars. This is a fairly broad category; within it, the most common type is red dwarves.
Group III machines
The most common for LANs is UTP category 5 or better cable.
The most common item listed in that category on eBay fluxes often and it's rather hard to discern but one of the most popular item happen to be GE oven parts.
The transition metals are the most common, and are found in the middle (groups 3-12) of the periodic table.
Metals / solids (around 75%)
Bright stars are rare, dim stars are common, so class M are the most common that we can see, but even dimmer ones are postulated to be even more common.