This has come up with Bronn having a duplicate.

Bronn comes into play and is given a duplicate, then another player pays the 1 gold to take control of him. That turn in combat Bronn dies. Who chooses to sacrifice the duplicate to save Bronn, the owner of the duplicate or the person currently in control of Bronn.

I say that whoever controls Bronn controls the duplicate and gets to choose to save or not. People have been telling me that whoever played the duplicate gets to make that choice.

Hoping to get an official Fantasy Flight ruling so that we don't hit this snag next game.

FFG has put out an official answer on this. It's in the Rules Reference Guide under "Duplicates" on p.7.

"A duplicate grants its controller the following triggered game ability: 'Interrupt: When the overlapping unique card would leave play, discard this duplicate to save that card. (Cannot be canceled.)'."

So the rules are clear - the person who controls the duplicate is the one who gets to use it to save the character.

And since there is absolutely nothing in Bronn's "take control" ability that says the person who takes control of Bronn also gets control of any duplicates or attachments on him, they don't. The person who marshaled the dupe still controls it - no matter who controls Bronn - so only the person who marshaled the dupe can use it.