When I'm gaming my cat will sit on my desk and grab my cheek with his paw to let me know he wants pets. If I don't stop and give him pets or don't give him the required amount of pets it escalates from him gently petting my cheek (hey you idiot, I want you to do THIS to ME), to him petting me with claws out, to him slapping me on the face, to angry headbutts.
If he doesn't want pets but just wants to be with me he'll just curl up in my lap with his head in the crook of my elbow and stare up at my face until he falls asleep. I love him so much, he's the absolute best cat.