Megatron. The receiving beast made it look easy last year, playing the game like a man among boys. He'll likely be gone by the end of the first round (maybe even top five) in fantasy football drafts. While he's the best WR available, the WR market is ridiculously deep this year, and not getting him won't kill your chances of winning.
There are five WRs going in later rounds who you can wait for and still win your league. Plus, it will allow you to double-down on the other positions in early draft rounds.
These aren't exactly "sleepers," a word that's lost all of its aura as fantasy football has become more prevalent with mainstream audiences. These are just players who could have big years and will give you enough points from the WR position to win it all.