Troy Brown - Started as a WR and played the following "Specialist" and "Situational" roles in regular season and playoff games:
Nickelback
Punt Returner
Kickoff Returner
Gunner
Gunner Blocker
Runningback
(Someone help me out, I'm sure he's been used in other positions.)
Troy has also been used as a QB in a preseason game.
Russ Hochstein has started at G & C and been used as a TE, RT, FB, and Wedge Blocker, not to mention blocking on Punt and FG teams. He's also the emergency Long Snapper.
Mike Vrabel has started at OLB, ILB, and DE, he's also played TE, DT, SS, wedge blocker, wedge buster, blocker/coverage on the Punt team, blocker on the FG team.
Adalius Thomas has started at DE, DT, ILB, OLB and played CB - in Baltimore, here he's just been used as a ILB/OLB/DE.
Wes Welker has started at WR for the Patriots and been used as a PR/KR. In Miami he also kicked FGs. I believe there was one or two other things he did for Miami.
Slater and Ventrone, though both are working hard and doing well, aren't in the running until they can do this in a real NFL game. For that matter, Ventrone is ahead of Slater, he's played SS and been on Special Teams in a real game.
The bottom line, just about every player on the team has cross-trained at another position, or been asked to play another role for a trick play. You have to love it.