hmmm tricky.
Many of mine are rather interational (esp as I am unlikely to twitch!) - Stella's Sea eagle is top. Harlequin duck not far behind, nutcracker too..
but british birds....
Top would probably be hawfinch - if they even exist
Crested Tit because I missed out when I went to Scotland this year
golden eagle
displaying woodcock
displaying Goshawk
displaying red throated diver
displaying black throated diver
lekking black grouse
Chough
little auk