Boo, bubba, or something related to his life.
When coming up with a nickname, think of his personality. If he's totally into sports, give him a nickname according to a sport he particularly enjoys. Or take his name and shorten it, like from...
-babe-baby-boo-SeXi-sExI bEaSt-handsome-hun-sweetheart-poo bear-teddy bear-cupcake-lollipop-baby bear-fuzzy wuzzy-good lookin:)))
Cute nicknames for Penelope are like Nelly or Penny.
Dani Annie Ani Didi (for girls) Danny (for boys)