If I think just about the sound, I like Leopold. Leopold II comes immediately to mind, though, and I find the name really unpleasantly dark and tainted as a result.
Leopoldine is a clunk fest. I often like these so-ugly-they're-cute feminizations, but not this time.
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PNL for boys: http://www.behindthename.com/pnl/116902/106592
PNL for girls: http://www.behindthename.com/pnl/116902/102654