Matthew Robertson, LD from the Edmonton Oil Kings intrigues me. Big kid at 6'4", roughly 200 lbs already, but a strong (but not I would call exceptional) skater. He uses his size, but doesn't fall into that game of trying to physically dominate every battle, instead using his intelligence and length to win some battles before they even start.
Robertson falls because of concerns over his offensive potential. And, it's true, he won't ever have the numbers of a Karlsson/Letang/Burns... but he is not, say a Lauzon-like black hole offensively. He has a good outlet pass and has a deceptive shot, in my opinion. I think 30-ish points should be about what to expect per-season. Basically, I think Robertson has the potential to be a better version of Dumoulin, if he hits his potential. On the low-end, I still see him making it as a 3rd pairing guy.
A mid round prospect I like is Ethan Keppen, LW from Flint. Another big kid at 6'2" ~210 lbs, Keppen plays a power forward game combined with an incredible work ethic. No matter the situation, Keppen always looks to be giving 100% effort. As with most power forward prospects, the worry is skating. I see enough that makes me think he will progress enough to be a legit NHLer, but others obviously disagree, as he is consistently ranked in the 3rd or 4th rounds.