A young scorer like Harrison Barnes would be my pick.
Good PGs are hard to get. So if we get the chance to grab Kyrie Irving, we should do it. I don't think Irving's rated as high as Derrick Rose or John Wall when they came out, though.
Adding Barnes to Bargnani, Davis, Amir Johnson, James Johnson, Derozan and Bayless would put Raps on the way to building a young and talented team.
At the moment, Raps sit at 5th overall but they're only slightly behind Sacramento for 4th overall.
Even picking at the 4th spot, Irving, Barnes are probably gone by then.