To me its Gray Fullbuster (Fairy Tail) and Launch (Dragonball) I just think those are terrible/uncreative names. What about you?
Gildartz, what the shit does that means?
It's a real English name but spelled differently. It's Gildart without the z or the s. Yeah, I think Hiro Mashima was trying to add German names such as Makarov and Ivan for a theme. Also, it's the name of the coat of arms. See this link.
As for worst names in Shounen, I would say Bra from Dragon Ball GT if it wasn't for the theme of naming children in Bulma's family after undergarments.