My kid was a "late talker" too - so first thing, I would say to relax. If the doctor isn't worried and your child is developing in many other areas, then there's probably no problem. Usually kids that are significantly delayed have delays in other areas. But if your child can hear, makes sounds, and does other things, he's just busy! First off, please note all that he DOES do: builds with blocks, climbs, walks, picks up things and feeds himself (fine motor skills), tries to roll or throw a ball, etc.
Next, be sure you aren't doing too much talking! If you fill in for him and anticipate all his needs, he really doesn't have to talk much. All his needs are met without verbal skills.
My son was 16 months and was into the whining stage - pointing at what he wanted or in its general direction, and sort of whining or grunting. Honestly, in frustration with all the annoying sounds as he pointed at a kitchen cabinet, I stared him down and said, "Honey, whatever you want in this world, you may have it, but stop that annoying whining!" (Risky to offer him anything, I know - but I wasn't thinking LOL!) That child looked right at me, and clear as a bell, said, "COOKIE!" Not Mama, not Dada. Cookie. After that, the avalanche of words started and he never stopped. I'm not saying that I "made" him talk - I think it was just fortuitous in many ways...but he was ready.
So I'd say to back off a bit, don't be afraid to say "I don't know what you want", and just wait for it. My pedi told me that he'd be talking by 18 months and if not she'd do some evaluation, but since he was active and growing and developing normally in every other way, she wasn't concerned.
So ask yourself why you are worried, or if you are just frustrated. And ask yourself if you're trying to keep up with other friends who nag you about your child not talking. Are you missing all the fun because you are too obsessed with talking? Believe me, in a year or two, you'll be frustrated that he won't shut up! So enjoy his many accomplishments and skills, and just wait for it.