As a Bug/Steel Pokemon, Scizor's single weakness of fire types is already amazing. Being able to learn Bullet Punch brings it to a whole new level, plus the ability Technician makes you wonder why you never used it before:
Bullet Punch (base 40 power)
plus Technician (x 1.5 boost)
plus STAB (x 1.5 boost) 90 power straight away.
Then give it a choice band to boost further and bring it to a devastating 135 power. This would be my ideal set:
Scizor @Choice Band
Evs: 252Atk 252Spe 4HP
Ivs: 0 SpA
I have seen Scizor wreak havoc in Competetive, and dominate entire teams. Add in the fact it can Mega Evolve, and it's design is TOTALLY BAD*SS then you got yourself a winner!