Alps SKCL/SKCM switches • Introduced in the early 1980s, Alps SKCL/SKCM series switches, aka complicated Alps, are a design classic with a range from delicate, damped tactiles to succulent clicks; and an impenetrable vortex of no return for wiki writers the world over.
Gateron switches • Gateron keyswitches are clones of Cherry MX keyswitches, and have a lot of buzz this year as the first worthy rival to the true Cherry. They have gained great popularity because of an innovation called "availability", that Cherry has struggled with, as well as a smoothness modern MX lacks.
IBM buckling springs • The famous, legendary, and downright notoriously loud IBM buckling spring is a mainstay of the mechanical keyboard realm. IBM made the king of click with an unusual design of switch where the spring buckles outwards instead of compressing. Buckling spring is at the heart of IBM's highly prized Model F and Model M families of keyboards.
Project Zealio switches • "Project Zealio" switches are a custom switch project by Zeal PC together with Gateron. The springs are gold-plate, the housings are fully transparent (not translucent), and you don't have to be <INSERT EXCLUSIVE CONTRACT COMPANY NAME HERE> to get them!
Topre switches • Love/hate: take your choice. There's no ignoring Topre. Topre switches power the "Only one Made in Japan electrostatic capacitive non-contact type keyboard in the world". They're either the most overpriced domes on Earth, or magic inside the greatest keyboards in the world today.
And the Wingnut for Best keyboard switch 2015, as voted for by the members of deskthority, goes to...