Hints:

Play as John McCarthey (referee):
     Enter  "Big  John" as a first name and anything as a last name in
career mode. When asked to save, choose "No" and exit.
Note: The name is case-sensitive. 
     Alternatively,  win championship road mode with a created fighter
to  unlock "Big" John McCarthy's body type, fighting style, voice, and
nickname in career mode.

Play as Card Girl :
     Enter  "Smile"  as  a  first  name and anything as a last name in
career mode. When asked to save, choose "No" and exit.
Note: The name is case-sensitive. 
     Alternatively,  win  UFC  mode with all 22 fighters to unlock the
Card  Girl's  body type, fighting style, voice, and nickname in career
mode.

Play as Karate Fighter:
     Enter  "Chop"  as  a  first  name  and anything as a last name in
career mode. When asked to save, choose "No" and exit.
Note: The name is case-sensitive. 

Play as Ninja Fighter:
     Enter  "Sasuke"  as  a  first name and anything as a last name in
career mode. When asked to save, choose "No" and exit.
Note: The name is case-sensitive. 

Play as Pro-Wrestler:
     Enter  "Mask"  as  a  first  name  and anything as a last name in
career mode. When asked to save, choose "No" and exit.
Note: The name is case-sensitive. 

Play as Kung-Fu Fighter:
     Enter  "Kung-Fu"  as  a first name and anything as a last name in
career mode. When asked to save, choose "No" and exit.
Note: The name is case-sensitive. 

Play as Kick Boxer:
     Enter  "Punch"  as  a  first  name and anything as a last name in
career mode. When asked to save, choose "No" and exit.
Note: The name is case-sensitive. 

Play as Ulti-Man:
     Enter "OCTAGON" as a hometown in career mode. When asked to save,
choose "No" and exit.
Note: The hometown is case-sensitive. 
     Alternatively,  win championship road mode on the hard difficulty
setting  with  any  fighter  to  unlock  Ulti-Man's  body type, voice,
nickname, and the "Octagon" location in career mode.

Play as Sumo Wrestler:
     Enter  "CIRCLE" as a hometown in career mode. When asked to save,
choose "No" and exit.
Note: The hometown is case-sensitive. 

Play as Street Fighter:
     Enter  "STREET" as a hometown in career mode. When asked to save,
choose "No" and exit.
Note: The hometown is case-sensitive. 

Play as Amateur Wrestler:
     Enter  "MAT"  as  a  hometown in career mode. When asked to save,
choose "No" and exit.
Note: The hometown is case-sensitive. 

Super fighter:
     At  the ability points screen in career mode, enter the following
stats for each attribute to max out all stats: Life: 23
Power: 51
Speed: 3 
Endurance: 9 
Stamina: 27 
Octagon Control: 77 
Ground Skill: 34 

Play as Bruce Buffer (ring announcer):
     Win  road  to Championship with a created fighter to unlock Bruce
Buffer's body type, fighting style, voice and nickname in career mode

Suitcase:
     Wijn road to championship mode with all 22 fighters to unlock the
"suitcase" location in career mode