My favourite airport is Liverpool John Lennon because it is a small nice airport with a good spotting area. Further more you get to walk up and from the aircraft when arriving or departing so no jet bridges. And easyjet operates from there.
Changi Airport is a no brainer, Incheon and Narita airport are also incredible places to be. Obviously my backyard, also known as Kuala Lumpur International Airport is a pretty nice place to be as well.
San Francisco International for the best airport in San Francisco Bay Area, Guangzhou Baiyun International Airport because it’s terminal is neat, Hong Kong International Airport because the approach my aircraft take is so awesome