I personally think that Pinsir's ability should be Hyper Cutter if you plan to Mega Evolve it on turn one. That way, if they start with Gyarados as an example, then it won't get the Intimidate lower. Its the only one of his abilities that will actually do something before he Mega Evolves on turn one. I would go with a set like this:
Pinsir @ Pinsirite
Ability: Hyper Cutter
EVs: 252 Atk / 252 HP / 4 SDef
- Close Combat/X-Scissor/Superpower
- Earthquake/Stone Edge
- Quick Attack/Knock Off
Pinsir has a lot of options. He can run Swords Dance or all-out offense, and can make up for a 4x Weakness with powerful fighting-type moves. All in all, he can be excellent addition to your team.
I'm SO SORRY that I've missed nearly the entire past month. Some serious stuff happened, and I'm really sorry to those here who were affected due to it. If I've forgotten anything I was obligated to do, PLEASE PM me.