In the UK, Porthcawl, Brancaster, The Sacred Nine, Swinley all score very highly on my personal clubhouse chart, and in very different ways. Of the larger houses, I have always really liked Hoylake and totally agree about Sunningdale. I also have a very soft spot for the 'expanded Victorian cricket pavilion' look which is still at the heart of (say) Westward Ho! and Harlech. Among newer clubhouse designs in the UK, I admire Portrush and Alwoodley (which received the ultimate accolade in UK architectural terms of being featured in Country Life), although I know this enthusiasm isn't universal. Basically, all these houses seem in keeping with their clubs, and create the right golf-centric atmosphere. Not over-grand, or even very smart (although one or two are), but in context absolutely fit for purpose, and, above all, welcoming.
PS Grateful thanks to Benjamin, for the lovely Shinnecock pix.