Walkers by Hiro Labo of Osaka Electro-Communication University's Department of Electro-Mechanical Engineering
First, here are some of Hiro Labo's more recent walkers.
LEGO Technic Tarantula!
Below is a great LEGO implementation of Chebyshev's walking mechanism:
And here's a miniature version of TrotBot with the heel/toe linkages included. It's amazing that Hiro Labo managed to implement the linkages in such a small version!
Next, below are some walkers that utilize the pressure of sublimating dry ice to push LEGO's pneumatic pistons:
WOW fast, right?
The following implementation of Klann's linkage looks like it mimics his patented version pretty closely, and the liquid nitrogen could be replaced by dry ice with similar performance (which is limited by the max pressure limits of the LEGO gear, not the source of the pressure)
For more details on how LEGO's pneumatic parts were used, see the following video:
Simplified Passive Walkers
Next, here are more simplified walkers that use gravity as an external force to walk passively.
Here's our favorite which utilizes a shaped foot. Tad McGeer's development of passive walking with knees is described here.
Notice how rubber feet were added to increase traction on inclines, or when pulling the robots.
Due to their small sizes the linkage dimensions of some of these walkers had to be modified somewhat to be built in LEGO, but they still walk fairly well.