For me it's probably Amsterdam Schiphol or Rotterdam The Hague Airport. I visit those two airports a few times a month in the sim.
Most of the time I fly with Transavia, because I fly with HV most of the time in real life and because I like flying for carriers like Transavia in Flight Sim
How about you? What airports do you fly to/from the most in Flight Sim and which airline do you fly for the most in Flight Sim?