Every flight, the first thing I do when I set is to rest my knees up against the person's seat in front of me, but not hard enough for them to notice. Every flight, that dipshit in front of me tries to recline but meets an impenetrable wall. The person then jabs the seat against my knees twice, thinking the seat is stuck. Then he/she turns and sees my knees resting there. I then get a dirty look, and an asshole huff. I then reply with, "next time bring a neck pillow"
Every so often I run into a dumbass that wants to check every 15 minutes or so, to see if I moved my knees, which I never do. It's only ok to recline when the seat behind you is empty or some kid is behind you. Other than that, pay first class/business class or GTFO.