This happens almost every year. Someone that most people have a day 2 or 3 grade on them ends up getting picked in Round 1. So, who is your surprise round 1 pick (or two). It should be someone that you haven't seen on any published drafts (or only a few) that gets drafted in Round 1.
For me, I'd go with Tyler Johnson, Minnesota. I could see a team like NO, Balt, Tenn, or KC pairing him with their other stud WR(s) to create mismatches. This guy gets open and is a redzone/TD magnet in a conference (Big 10) with a lot of good CB play. If not Johnson, then WR Edwards from South Carolina. A seemingly do-it-all WR who would be a consensus 1st round pick if not for injuries, IMO.