nie- key.
The president of Nike actually sent out a "definitive" pronounciation of it... "Ni" like in "nine" and "ke" like "key Ni-key
It depends where you are. Where I'm from, we say n-eye-kh, but I've heard it pronounced n-eye-key.
Ni-key.
N-eye-key LOL
Nai-key
ny-kh
"nike"
"Nike"