I have one of the most common (first)names in Finland, Niko, but it's also spelled Nico, both are right in one way but here's some history for you who don't know this.
Finland is a bilingual country which means we have two mothertongues according to law, finnish and swedish. The K in the name Niko is often for those whose main language is Finnish while C is for the swedish (not always, just a thumbrule you can go according to). Here's the problem, Finland is mainly split in two parts, the finnish and the swedish "sides", but I am lucky since I speak both languages equally 'cause my moms mothertongue is swedish while my father's finnish. Well they decided that my father would pick the name of their firstborn (me) and that's why my name is with a K. But the reason everyone spells it wrong is because we live in the swedish parts of Finland. It's no big deal but I have just started to get pissed when people spell it wrong because my name is a pretty big part of me ^^. No one sais it wrong thou...