I'll cut against the grain with a few:
SELL
Trent Richardson -- Yes, there's alot to like here, but IMO people are totally ignoring the very real downside here -- namely that he ends up being the non-dynamic guy we saw last year. Someone (probably five+ someones) in every league thinks he's the slam dunk #1 player overall, and I think it would be a smart move to throw him out there to start a bidding war and see what type of king's ransom he would bring. Don't dump him obviously, but if you can get an AJ, Dez, Martin, McCoy type cornerstone ++ I'd be strongly considering it.
David Wilson -- I actually like Wilson, but the hype train is out of control here particularly after the Brown injury, which is actually pretty irrelevant to his long term value. There are people that see him as a top 5, even THE #1 RB moving forward -- if one of those dudes is in your league and will pay for the upside, I'd cash out.
Lamar Miller -- Another guy who has a group of true believers that are ignoring the downside. He went as the main component in an AJ Green deal in a solid league I'm in. He's been acquired for guys like CJ Spiller in the dynasty trade thread, and no one batted an eye. That's absurd for a 4th round RB in a bad situation who couldn't beat out a scrub like Daniel Thomas last year.
BUY
Percy Harvin, Michael Crabtree, Kenny Britt, Ryam Matthews, Darren McFadden, Josh Gordon, Justin Blackmon, etc -- guys with difference making talent that are (sometimes massively) discounted due to injury and/or suspension. Almost always good value to be had...