Good thread, excited to see what some of these guys with more experience than me have been up to. As for me there are two times that really stand out. The first was staying at my best friend's grandparents house. They had a half dozen outdoor dogs of varying shades of mutt (the benefits of living rural) and the grandparents had already gone to bed. My friend had gone to take a shower or something where I knew I would have ten minutes or so of privacy so I went out to the driveway, quietly called the dogs over to me, and knelt down. I was too paranoid at the time to try anything penetrative so I just unzipped my pants and pulled my cock out. I don't know if it was just because they were all riling each other up or what but they went nuts: tails wagging, shoving each other out of the way jockeying for position to lick my cock. I've never met a single dog since, much less a group of them, that were so into lickjobs. So I spent a minute or two on my knees in the dark on a balmy southern night, trying to stay quiet while three dogs at a time fought for the privilege of my cock. I came so hard, all over tongues, muzzles, and fur., then zipped back up and stumbled inside.
Next story is at my parents' farm, they have an equine rescue. One of their clients was a male donkey who I topped regularly all through college. Super sweet and let's just say, just the right height. But I digress, anyway I had decided one day while my parents were out that I was going to try anal with one of the geldings instead, variety being the spice of life and all that. So I had everything set up, standing on the bucket, cock out and lined up, and I hear the donkey yell from across the field. He comes sprinting across the field, rears up at the geldings, kicks yells and chases them all off, then walks right up to me. He turns his rear towards me and just stands there waiting expectantly. Obviously I gave him what he wanted, but if I hadn't experienced an animal be jealous that someone else was getting fucked instead of them I don't know if I would have believed it.