While you can be creative, one of the drawbacks of getting too creative is that it can be difficult to determine who actually has the authority to enter into a contract on the LLC's behalf. As a result, you'll see titles that try to merge both worlds, like "president and chief imagination officer." That way, you state a clear chain of command (handy when you're dealing with fussy institutions like banks), but show a little edge (to avoid seeming stodgy).
When in doubt, it is safest to go with the traditional titles you see with corporations, such as president, vice president, secretary and treasurer. You can always find a way to spice up the marketing but an unclear title could cause more problems than it's worth.
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