What freewheel mechanism designs are used in bicycles? What are the various freehub mechanism designs that have been designed and or put into production? (doesn't need to have been made necessarily!)

A good post will contain:


A description of the design, ideally with images or technical drawings
Companies that have used the design or who created it
Advantages and disadvantages
Original design/incremental improvements that have occurred


Designs known so far (those with a post are linked):


Standard Pawl and Ratchet (and variants)
Star Ratchet (DT Swiss/Chris King)
Sprag Clutch (Onyx)
Roller bearing clutch (true precision stealth, shimano silent)
'Cam plate design' (American Classic) possibly a combination of pawl/ratchet and star ratchet.


I'll be going through and trying to fill in for designs that I know of, but feel free to post an answer if I haven't already. Also feel free to post an answer for a design not listed here! And provide additional info for already posted designs!
Standard Pawl and Ratchet Design
This design is by far the most common on bicycle freehubs, and as such the least expensive to employ.
Mechanism
In it's simplest form, this design consists of a surface that is toothed and a pawl (which is a lever that engages the toothed surface and only allows movement in one direction).

In a bicycle this design is typically inverted, the pawls are on the freehub body and they engage a toothed surface on the interior wall of the hub.


a basic animation of the mechanism in action can be found here. In this design, some tension must be applied to the pawls to constantly force them outward into the body of the hub. (This is also where the buzz or click comes from in this design, from the pawls being forced over the teeth on the ratchet surface) This is usually accomplished by leaf springs, small coil springs, and/or a metal ring.

this design utilizes leaf springs

coil springs

technical drawing of a mechanism utilizing a metal ring
Advantages and Disadvantages
Advantages

Common and inexpensive
Easy to service

Disadvantages

Lower degree of (quicker) engagement limited by physical constraints. A lower degree of engagement requires smaller teeth contact surfaces and pawls which become weaker/can wear more quickly. (see below for some clever workarounds)
Prone to failure due to weakening springs or grease thickening with cold/age (&quot;nothing happens when I pedal&quot;)
In it's most basic design, relatively high degree of (slow) engagement
Prone to wear as teeth and pawls are constantly in contact

Variations
Many designs will use more than one engagement tooth per pawl, allowing smaller teeth and more points of engagement (lower degree of engagement). These small teeth are more prone to wear. Halo supadrive employs 120 points of engagement for 3 degree engagement

Halo Supadrive utilizing 120 points of engagement
SRAM's Double Time design utilizes four pawls in opposed pairs. The pairs are offset slightly, causing only one pair to engage at any time, but gives their 26 tooth ratchet 52 points of engagement for 7 degree engagement.