my nemesis birds for my state include American Bittern, Painted Bunting, Brown-headed Nuthatch, Black-throated Blue-warbler, American Oystercatcher, Cape May Warbler, Peregrine Falcon, Semipalmated Sandpiper, Sedge Wren and many more ?
For the ABA area, my biggest needs are (??) White-breasted Nuthatch, White-throated Sparrow, Pine Siskin, Common Merganser, Dark-eyed Junco, Common Raven, Hairy Woodpecker, Red-breasted Nuthatch, Field Sparrow, Rose-breasted Grosbeak, Common Goldeneye, Warbling Vireo and more, and basically every bird west of the Mississippi River.... (Great-tailed Grackle would be a lifer, you get the point ?)
If I had to choose one bird to see above all the rest, I'd pick Greater Sage-grouse.
And, yes, I haven't seen a Song Sparrow in 9 years... here's hoping I see one this winter!