Have you ever seen a bird dive bombing a cat over and over?

Yep, for a minute. Then I watched a cat eat lunch.

Yes, particularly mockingbirds who are territorial to the point of putting their own lives in danger to aggress anything they consider a threat. They’ll divebomb hawks too.

The bird in this gif is a mockingbird, for example (warning: the video does not end well for the bird): http://i.imgur.com/gRkaq.gif

Large groups of blackbirds will work together to harass threats like hawks, owls, and cats, too.

Yes. And I laugh because my cat is an asshole.

The bird had a nest near by @Aster. She wasn’t just teasing or having fun.

Yes. I’ve been dive-bombed by robins.

Oh sure, bunches of times.

Closest I’ve gotten is watching a friend’s two pets, a parakeet and small dog, play a game I called swoop-follow-nip-bark.

When released from his cage, the bird would fly around the room, land right behind the dog, and follow him around, periodically nipping at his tail. The dog would turn around and bark a couple of times but never attack the bird. The bird would then fly up, land again, and then the whole game would repeat until one or the other pet got tired. It was hilarious to watch.

I’ve seen birds do this to cats and squirrels. Also squawking at them. It seems to be about trying to get them to go away from nests and/or bird food sources.

Not yet, but I have seen a wasp chase a spider down a web strand.

I have, yes. My cat goes in the garden and it’s not unusual to see a few birds swooping him. Not close enough to get caught, but to alert other birds he’s there. He’s like the honey badger. He just gives them a look of disdain and carries on.

I was fishing once in a swamp. There were many Cyprus trees around, but only a few growing strait out of the water. There was a large Osprey nest on top of one. About 20 yards away, there was a nest by a very small bord (not sure what it was,a sparrow? )
Every time the Osprey came flying back to it’s nest, the smaller bird attacked it. This happened about 12 times while I fished the area. I was shocked at the small bird even having the courage to attack a much bigger, and much more dangerous bird. But… The Osprey just got beat up repeatedly. Once, it lost a fish it came back with. Since then, I’ve always chuckled about those two neighbors. They must spend the bulk of every single day fighting. I wonder if one day, the osprey got sick of it, and just killed the little bird…

Can’t say that I have.

I saw a group of mockingbirds dive bomb a cat, which eventually took cover under a car.

And live? no.

Crows and Jays are notorious for this also. I’ve seen them run off perceived predators many times, including humans. Very aggressive territorial defenders.

Canadian Geese attack pretty much anything…

Yes. There are many hawks and eagles here and small dogs get picked up sometimes.