[Overview]

Fearsome sweeper and strongest Bug-type in NU
Incredibly hard to wall because of its huge Attack and great coverage options
Two great abilities to help it sweep
Fairly fast, though most of the common offensive threats in NU are even faster
As a sweeper, faces competition from Scolipede which is faster and almost equally powerful thanks to Megahorn
Pinsir sets itself apart with Mold Breaker to beat checks and counters that Scolipede loses to as well as priority to beat faster Choice Scarf users and other priority users

[SET]
name: Sword Dance
move 1: Swords Dance
move 2: X-Scissor
move 3: Earthquake
move 4: Quick Attack
item: Life Orb / Lum Berry
ability: Mold Breaker
nature: Adamant
evs: 252 Atk / 4 Def / 252 Spe

[SET COMMENTS]

Pinsir runs an effective Swords Dance set thanks to its high Attack stat, ability Mold Breaker to get past counters, and priority to get past NU's most common Choice Scarf Pokemon
After a Swords Dance boost, incredibly powerful and capable of taking down some of the most common physical walls
X-Scissor is Pinsir's strongest STAB, and it handles some of the more common defensive Pokemon, such as Musharna and Tangela, that other sweepers struggle to beat
Earthquake takes out the Steel- and Poison-type Pokemon that resist its STAB, as well as most Pokemon with Levitate, such as Misdreavus and Weezing, which would otherwise wall the set
Quick Attack is for priority to hit faster Pokemon, such as Jynx, Primeape, and Charizard

[ADDITIONAL COMMENTS]

Adamant>Jolly because the only Pokemon Jolly lets you outspeed are +Speed base 80s and +Speed base 85s, both of which are fairly rare
Life Orb helps get some KOs at +2 and helps Pinsir's immediate offensive presence, but Lum Berry can keep an untimely burn or poison from ruining Pinsir's sweep
Moxie's only advantage would be to get the OHKO against Primeape with +3 Quick Attack, which is crap compared to the utility of Mold Breaker
Pinsir greatly appreciates Stealth Rock support to help it get the OHKO at +2 against the likes of Swellow and Charizard with +2 QA and Lickilicky with +2 X-Scissor; Regirock can spread paralysis, take on Normal-, Flying-, and Fire-type attacks that threaten Pinsir, and set up SR
Stealth Rock also helps it wear down Flying-types that wall Pinsir
Spikes support can help Pinsir get the KO against Piloswine and Seismitoad, and Garbodor can set them for Pinsir with Pinsir getting rid of the Psychic-types that threaten it
Pinsir has troubles dealing with Alomomola even after a boost; Pokemon such as Ludicolo and Eelektross make good partners to eliminate it
Flying-types wall this set, so offensive Electric- and Ice-types can help handle them; Rotom-A and Jynx are good examples of this

[SET]
name: Choice Scarf
move 1: X-Scissor
move 2: Close Combat
move 3: Stone Edge
move 4: Earthquake
item: Choice Scarf
ability: Moxie
nature: Adamant
evs: 252 Atk / 4 Def / 252 Spe

[SET COMMENTS]

With Choice Scarf Pinsir becomes a dangerous revenge killer and late game sweeper
With Moxie and its good Speed, if this set can revenge kill one Pokemon, it can often either heavily damage or sweep the rest
X-Scissor for STAB and does great on Psychic- and Grass-types, such as Gardevoir, Musharna, and Serperior.
Close Combat is just as deadly as X-Scissor and does quite a number to Lickilicky, Piloswine, and Probopass.
Stone Edge hits Flying- and Bug-types such as Scolipede, Braviary, Charizard.
Earthquake patches up hitting Poison-types such as Garbodor and can act as an in-between option between X-Scissor and Close Combat.

[ADDITIONAL COMMENTS]

Jolly nature only allows you to outpace +2 Modest Gorebyss and positived nature Choice Scarf base 80's, but those are rare in this metagame.
A Moxie set with Life Orb is a viable option since the easiest way to wall Pinsir is by resisting whatever move it locks into
Since this set can be easy to wall before it gets a boost, it forces many switches, especially into the Flying- and Fire-types that can take its STAB, so Stealth Rock support can be useful to wear down its checks for a sweep later on
Most physical walls in the tier give this set issues, so wallbreakers can help to remedy this issue; mixed Eelektross, SD Charizard, and Gothorita can all beat walls well
Vulnerable to faster Choice Scarf Pokemon, such as Primeape, Charizard and Jynx; Kangaskhan makes a great partner since it can defeat those Pokemon with priority

[Other Options]

Choice Band
Salac Berry
Endure + Reversal
Sub+Focus Punch
Bulk Up
Stealth Rock lead with Mold Breaker, though it loses to many common leads
Knock Off to cripple Eviolite users such as Misdreavus and Piloswine

[Checks and Counters]

Ghost-types such as Misdreavus and Golurk take little damage X-Scissor and the former can use Will-O-Wisp while the latter threatens with a poweful Shadow Punch. They must be wary of taking on a +2 Pinsir since Earthquake does a massive amount to Misdreavus and OHKOs Golurk.
Alomomola can counter both sets if they haven't accumulated any boosts and can Toxic stall them
Any Pokemon that can take a +2 Quick Attack easily can deal with Pinsir; examples such as Haunter, Rotom-S, and Tauros
Kangaskhan can deal with weakened Pinsir with Fake Out + Sucker Punch combo
Any Choice Scarf Pokemon faster than Choice Scarf Pinsir such as Charizard and Rotom-S can revenge kill Pinsir with their STABs
Regirock, Armaldo, and Metang can take any hit while striking back with their STAB moves