Nickel
Nickerson
Nicki
Nicki-Baby
Nickleby
Nickles
Nick-the-Cat
Nicky
Nicky Jean
Nicky Legs
Nico
Nicodemus
Nicolas Fosbury
Nicole
Nicolette
Nicolodeon
Nicorette
Nielsen (after Rick Nielsen, the Cheap Trick guitarist)
Nie-Ma-Imie (Polish for "has no name")
Nietzsche
Nieves
Niffer
Nifty
Nigbee
Nigel
Night
Nightcrawler
Nightcrouler
Nightmare
Nightshade