Unless one of the top 6 fall, my choice at 7 is Victor Eklund. Just go get the legitimate top 6 forward. He's fast, competitive and skilled and producing against men and also in the WJC U20. Bonus is that he will play in the NHL sooner than other options.
Martin would be my next choice. He at least plays with power and has pretty very high floor. It is easy to see a 30-30 guy with physicality and leadership here. The comp going through my head that is giving me reservations though is Luke Kunin.
O'Brien scares me. If Lardis is not on that team (71 goals!) then O'Brien scores 80 points. Still good, but mid-late first round territory. I don't want to pick a forward in the top 10 that does not have power or speed. We also have not seen this production translate to a different context, like an international tournament. I think O'Brien is more Ryan Suzuki than Nick Suzuki.