The only two Pokemon that have Prankster, Taunt and Fake Out are Sableye and Liepard.
Out of those two definitely go for Sableye.
Sableye @ Leftovers
EVs: 252 HP / 252 Def / 4 SpD
- Foul Play/Fake Out
This is nice Taunting Set for Sableye to use. I wouldn''t really recommend a Fake out on Sableye with Taunt as well to be honest. Sableye can benefit from other moves - Fake Out is pretty limited in use too. Fake Out isn't a bad move but its better on an offensive Sableye. But this is you team and your choice, so do what you feel best is.
Although no equipped with Fake Out another good Pokemon is Thundurus
Thundurus @ Sitrus Berry
EVs: 244 HP / 108 Def / 64 SpA / 72 SpD / 20 Spe
- Thunder Wave
- Hidden Power Ice
A bulky Thundurus with Taunt and Priority T-Wave can seem a bit of a pain to take out. Taunt prevents Thundurus or his teamates being crippled and stops TR Teams.
Good Partners for Greninja
Greninja being frail and fast is more viable going all offensive. You can side Greninja with :
M-Kangashan - Fake Out + Pressure on opponent with Parental Bond
M-Mawile - Being Bulky it can take some hits and Greninja heavily threatens and Ground Pokes
CB Talon Flame - Brave Bird. Types that don't resist cannot hang around with this guy on the loose
M-Medicham - Fake Out can give Greninja an opportunity to deal with threats.
Rather than Mat Block or Knock Off go in for Gunk Shot or U-Turn.
Life Orb might also be better than Choice Scarf as you'll only stay one type and doesn't make Protean as threatening.