Copenhagen - because it has such thought through structure, has great shopping, somehow feels cosy (think its the clever floor use, mainly wood), has good food selection and is quick and easy to navigate and get around even though it is not a minor airport.
Zurich - since they renovated it it feel like such a treat to be there, excellent "airport feeling" in the best sense of the word.
Charles de Gaulle - ok, i will not argue against its maddeningly stupid passenger flow planning, the lack of logic for navigating around the place or the sign either pointing you to a dead corner or simply not being there at all. But its a freaking lovingly piece of concrete! I forgive a lot of frenchy logic when it comes to my favourite grey animal. Touch, feel, love!
Bromma - Stockholms very small central, mainly domestic and governmental flights airport. Supreme piece of scandinavian functionalistic design, with incidentally also makes the airport being extremely userfriendly. I heard someone wants to tear it down and build housing; shame on someone.
Other nice airports from top of head: Munich (white, spacious, clean), LAX (well, a little disappointing actually, bad shopping and boring now that i think of it), Vienna (nice), Cologne-Bonn (the new terminal is not bad, and very peaceful at night), Hahn (Ryanairs not-really-Frankfurt landing field is surprisingly good, and getting better everytime i come by at that. Soon getting to big for its own good though - what about walking five min to the bus that used to stop 50 m from the luggage belt?)
Airports to avoid, avoid, avoid
Frankfurt International - so bad. HUGE, lots of walking (that tunnel, anyone?) standardised shopping (1 gin,1vodka,1whisky,top5 perfumes, Milka), ugly, unfriendly, uncomfortable, ugly, did I already say lots of walking and no pleasant waiting area? Avoid.
Heathrow - someone here said it "feels a little dirty", someone was onto something. Add messy, smoky, old, and a seemingly bad or just understaffed organisation keeping the place running and you get my feeling for this dump. Like the quick train connection though.
Shiphol, Amsterdam - so damn square. Bores me.
Cointrin, Geneva - maybe unfair to take up here, but it is just so small and provincial, you'd expect at least a decent place to have coffees in the airport of one of the wealthiest cities of Europe.