Ratchet & Clank: Size Matters

A secret set of armor is just a combination of pieces from different sets. Each combination of armor has a different effect on your melee attacks. You have to equip the set and leave the menu (Possibly hit a continue point). I'll list a some examples.

Wildburst Armor:
Sludge Mk.9 helmet with Wildfire body, gloves and boots.

Triple Wave Armor:
Wildfire helmet, Sludge Mk.9 gloves and Electroshock body and boots