Five trades that could happen in the 1st round (my opinion only):
49ers/Buccaneers:
San Francisco is sitting at #30 and have big needs at DB. They also have several draft picks after the 1st. They have two in the second and three in the 3rd round, so they have the picks to make a big move. A big jump could net them Gilbert, Dennard, or Clinton-Dix. Tampa Bay has several needs and a trade down could help fill those. They would have to be intrigued at the notion of getting at least an additional second and third round selection.
Jets/Titans:
Even with the signing of Eric Decker, the Jets still need to get a top notch WR in the draft. Watkins is probably out of the question, but they can trade up to get Evans or Beckham if they choose. If Barr is off the board by the time the Titans are on the clock, trading down to gain an additional pick could interest them. Tennessee does not have a third round pick.
Browns/Cowboys:
This would involve Cleveland's pick at #26. If the Browns go QB at #4, a WR would be next on their checklist. There is a chance that all the big four receivers (Watkins, Evans, Beckham, Lee) could be off the board, so a trade to get one of them would be necessary. They could also look at OG Zack Martin. The Browns also have multiple picks. They have seven in the first four rounds. The Cowboys have several needs, especially on defense. Dallas hardly ever stays in the same slot on draft night. If either Donald or Clinton-Dix are still on the board, they could stay at #16 and pick one of those two. However, it seems likely both will be gone, perhaps upping the chances of Dallas trading down.
Saints/Cardinals:
To me, the player who could be a perfect fit for the Saints and their needs is Alabama LB C.J. Mosley. However, with teams like the Packers Eagles, and Browns ahead of them, the chances of them getting him while staying at 27 seems remote. A trade to #20, barring any of those teams trading up, put them ahead of those three. Arizona could move down seven spots and still be in position to fill a need. Gaining a pick would also be a plus.
Patriots/Chiefs:
New England has needs at DE, DT, and DB. While they can fill that need at 29, they may look to go up and seek quality. The Chiefs have a huge need at WR, but the top four will likely be gone and others picked at 23 could be a reach. Also, the fact Kansas City doesn't have a second round pick could be a motivation to trade down.