I picked two of the standing Minecraft mobs because the ones on four or more legs don't fall off when the balance platform shifts.  I'm playing around with putting shorter mobs on really tall bases and I might upload some more options later.

To make them more prone to tipping over use a height modified to increase the infill for the top 50% of the model.  I did this and it makes for a exciting and challenging game.

Use a fine tip black sharpie to enhance the faces.