Hashing-out the definition of what it means to be a "Gatekeeper" and "Journeyman"... "Contender" and "Prospect", etc...
**link to May 2012 Updates**
Champions - elite fighters with a Championship Title; excluding relatively less accomplished "Champions" from certain promotion orgs
HW - Overeem, Cigano
LHW - Hendo, Jones
MW - Anderson
WW - GSP
LW - Melendez, Frankie
FW - Aldo
BW - Cruz
FlyW - Ian McCall, Yasuhiro Urushitani
Contenders - fighters ready to fight for a (elite) Championship
HW - Cain, Barnett, Werdum, Frank Mir
LHW - Rashad
MW - Sonnen, Lombard, Okami
(Lombard has a Title but isn't quite "elite")
WW - Ellenberger, Condit, Diaz
LW - Benson, Aoki, Chandler
(Aoki, Chandler have Titles but isn't quite "elite")
FW - Kawajiri, Hioki, Patricio Freire
BW - Bibiano, Urijah, Barao
(Bibiano has Titles but isn't quite "elite")
FlyW - Formiga, Joe Benavidez, Demetrious Johnson
Gatekeepers - fighter who separate the true Title Contenders from everyone else; who they themselves aren't likely to win a Championship
HW - Minotauro, Roy Nelson
LHW - *Rampage(new role as GKer), Forrest(lame-duck GKer), Minotoro(lower-level GKer)
MW - Nate Marquardt
WW - Diego Sanchez
LW - Clay Guida
FW - Diego Nunes
BW - Jorgensen, Mizugaki
FlyW - Yamaguchi
Top Prospects - fighter who have separated themselves from the crowd, but who has yet to prove their mettle on the Championship contender-level
HW - Daniel Cormier
LHW - Gustafsson, Mo Lawal, Mousasi, Phil Davis
MW - Mark Munoz
WW - Rory MacDonald, Johny Hendricks
LW - Nate Diaz, Barbosa
FW - Pat Curran, Koch
BW - Zach Makovsky, Michael McDonald
FlyW - Darrell Montague, John Dodson, Ulysses Gomez
Journeymen - fighters who will never be Champs or even true Contenders; basically failed Prospects who still manage to have a successful career in the sport; stepping stones for Prospects/Up-n-comers
HW - Ben Rothwell
LHW - Stephan Bonnar
MW - Chris Leben, Kendell Grove
WW - Brian Ebersole
LW - Yves Edwards
FW - Leonard Garcia
BW - Kenji Osawa
FlyW - Mitsuhisa Sunabe
Up-n-comers/Prospects - younger fighters (but also some resurgent veterans) with promising futures who have yet to truly break-out
HW - Stefen Struve, Shane del Rosario
LHW - Stanislav Nedkov
MW - Ronny Markes, Alen Belcher
WW - Bahadurzada, Douglas Lima
LW - Patricky Freire, Caros Fodor
FW - Diego Brandao
BW - Ed Dantas
FlyW - Dustin Ortiz, Haruo Ochi
Tomato Cans- fighters who serve mostly as filler; may not even be a stepping stone; generally hover around a 500-record or worse
HW - James Thompson
LHW - Jason Guida
MW - Phil Baroni
(currently)
WW - Waachiim Spiritwolf, < Pete Spratt
LW - Junie Browning, < Rob Emerson
FW - Doug Evans
BW - Bryan Goldsby
FlyW - Neil Seery
All fighters generally fit somewhere in one of these categories but not all.
Some guys like Forrest Griffin might be "Gatekeeper" level at this point in their career, but who don't really do actual gate-keeping (don't fight/test top prospects)... but they're better than your everyday journeymen. And so forth.
P.S.
Some fighters like Michael Bisping or Thiago Silva seemingly become perpetual Top Prospects, where they get repeated chances at proving themselves to be Contenders, but don't quite make it all the way.
There are also fighters like a Frank Mir who refuse to become/remain Gatekeepers, but who may not
truly be Championship Contenders either (we'll see).
*tough time settling on example of Gakekeeper at LHW