(not OP, have regular robo mower) Animals are no problem, they get out of the way themselves. Children leaving toys out (or socks), or branches that have been blown off trees, or chestnuts - those make for some scary noises.

I'm no expert, but Cats and Squirrels would be pretty good at hearing and seeing danger, even feeling vibrations nearby. I doubt they'd get caught by a lawn mower at walking speed.

I would like a tutorial on how to make one that can chop up the neighbor's cat please.