Most of the most wanted UK species being mentioned here I've seen at their best (eg Lap Bunt, Red-throated Pipit, Wilson's Phal), Grey Phalarope being the major exception. If I've seen the full plumage abroad I'm not too bothered about getting it in the UK, although I might bend that rule for a Bobolink.
What I am missing, and would like to catch up with some day, some place, are a Red-breasted Flycatcher with a red breast and a Barred Warbler with bars.