Times were good with megas, but both before and after there's absolutely nothing Pinsir does that heracross and scizor/scyther don't do better. He's too slow to sweep, lacks the resistances to make use of what's really only middling bulk, and has no strong options to compliment it's decent attack. So for a bug STAB that can help it overcome its weaknesses (not necessarily signature, Vikavolt Drapion Ariados and maaaaaaybe Durant could get it too):

Mandible Mash: 80/90 BP, 10 PP. Lowers target speed by one stage.

Pinsir's bug type movepool is just so bad while heracross and pinsir hang out with megahorn and technician bug bite, even when it had the mega i rarely ran X-Scissor, it's only decent bug stab. Without aerilate pinsir just does not do enough damage for how slow it is, this would give it a tool to punish and then outspeed weaker switch-ins and let it maybe find a niche in N/RU.