DS will be 1 at the end of the month, and he can't clap!!! We've just started Monkey Music (baby music class) and he's the only one who can't clap. In situations where he would clap, he waves instead - goes up and down rather than hands together. Been like that for months!
Also he has no words, not even Mama and Dada. He says those syllables, but more like mamamamama, and not even really in context. If he is calling us from his cot he will just make random noises, not ma/da. He definitely understands words though, you can ask him to go get a ball/book and he will. He loves books. I think I don't do enough nursery rhymes/animal noises with him.
He is walking though and very happy and busy, so I've always just thought he had his priorities focussed on the physical stuff. But the HV at his year check last month said they'd be worried if he's not Mama and Dada-ing by a year 
Believe it or not I actually think of myself as quite a relaxed, level-headed parent, but it seems I am going through a fretful phase! 