First Hint: We are unstoppable. We are as immovable objects in our path. We will plow through anything without a care in the world, nor a thought, whim, or objection. Not even fire or the mighty oak can stop us as we make your journey a treacherous one.
Round 29 -- Zelda Classic -- Xyvol
http://www.armageddongames.net/triforcequest/boulder.gif
It was either that or traps, and traps can be changed to stop at unwalkable combos.
How about we use the example category and go with Animals?