I was fairly recently looking through some of my old photos and noticed in one photo I'd taken of a Red-winged Blackbird, a Virginia Rail I had not noticed was clearly visible in the background. That was two years before I got my lifer one.
I've lived in range for Eastern Whip-poor-will all my life and seen it exactly once, briefly as a flyover. Meanwhile I spend a couple nights in range for Dusky Nightjar and get incredible views of it easily.
I almost went an entire three week trip to Costa Rica without seeing a single trogon. Then I finally nabbed two species one of the last days I was there.
I've gone after Kentucky Warbler in the ABA area a number of times, most notably this summer when I spend several days looking for a Wyalusing State Park, where I heard quite a lot of them and never saw one. Then I see one all the way in Costa Rica.
I saw multiple King Vultures before my first Roadside Hawk.
Great Curassow was in the first 25 birds I saw in Costa Rica and therefore saw it before quite a few very common species (Crested Guan as well but that one fells less notable).
My lifer Brown Booby and American Flamingo were in Wisconsin.
The first bird of prey I saw in Florida was Crested Caracara. Yes, before a Black Vulture.
My first Limpkin was in Florida and not some bizarre vagrant.
My lifer Pale-billed and Lineated Woodpeckers came at exactly the same moment, when they both flew into my line of site at the exact same time.
My first non-woodcreeper furnariid was Streak-breasted Treehunter.
Not a bird, but my first wild venomous snake was a coral snake slithering over my foot in Florida. That's why always wear shoes in a pine hammock.