I keep running into a blue heron in the back yard. I have a decorative pond with goldfish and I'm pretty sure it's stalking them at times. A few weeks ago a cop saw it standing on top of the pond's waterfall and didn't even try to arrest or question it. I suppose the heron appeared to be minding his own business so the cop didn't have probable cause, but when I see a heron standing in a pond full of six-inch goldfish my mind would scream "crime in progress."
Yes, my old pond in the back garden suffered from heron predation too. One of the local grey herons must have spotted it while on his rounds and added it to his usual patrol. So much for the fish population.
Other than that, I wouldn't say there's a lot of "unexpected" wildlife in my garden. Some young foxes make a patrol of it most nights, and we used to have hedgehogs until they picked a fight with the cars. At university, muntjac would sometimes walk past my window, which was always a nice surprise, and of course there were my bats. I say "my bats" because I grew quite fond of them. I think I was attracting insects, because they tended to swoop around me, far closer than I thought they'd come.