One of my cats (always a house cat) will literally run to me for help if it's anything bigger than a fly. He got scared of a dust bunny and came crying at one point.
On my my barn cats got let into an attic that we suspected had rats in it. She wouldn't come down for days till she finished the job. One day we were on the porch, and heard scrambling on the roof. Nex thing we know she's taking a 12 foot dive from off the top rope with an 8 inch rat in her clutches.