Mechanisms

Pictured below is the slotted yoke drive. Starting from the position pictured, the disk rotates counterclockwise with a seemingly constant speed, and the peg pushes the slot and rod to the right. The rod then pauses momentarily as the peg travels up the slot. The peg pushes the slot and rod to the left. Then, the rod pauses as the peg travels down the slot. The motion repeats. Thus, the rotational motion of the disk and peg is translated into the back-and-forth linear motion of the rod. I like this mechanism because at first sight, its movement was confusing; however, after a minute of watching the video, I understood how it worked and thought it was awesome that purely rotational motion could create purely linear motion. This mechanism has been used in many internal combustion engines. I can also imagine an application for it in which bike pedals power the turning of the disk in order to provide linear motion for some specific purpose.

"The location of the piston versus time is a sine wave of constant amplitude and constant frequency, given a constant rotational speed." (Wikipedia)

Sources:
http://kmoddl.library.cornell.edu/model.php?m=446&movie=show
https://en.wikipedia.org/wiki/Scotch_yoke