Whenever an assault or pyrotech specced Vanguard/Powertech gets the proc for a free railshot/high impact bolt, the character laughs out loud letting the player know their talent just procced
Assassins and Shadows have the same talent for our backstab move, except we don't have any kind of indicator. (Actually, theres a VERY small effect that you can barely see if you're zoomed in, let alone zoomed out and fighting).
We're basically forced to either stare at our buff bar or just fight normally and pray. I don't think its out of the question to give assassins an evil laugh or shadows a confident "Hmph!"