Well there are only three moves with 40 PP (64 max) that do damage, all with 100% accuracy being: False Swipe, Hold Back (event exclusive), and Rapid Spin. However, these moves only have base powers of 40, 40, and 20 respectively. The good news is that False Swipe and Hold Back are extremely useful for catching shinies in-game without fainting them, and nearly any Pokemon can learn False Swipe through the TM in ORAS.
Looking onwards into the list, moves 35 PP now (56 max) that do damage include: Wing Attack, Tackle, Metal Claw, Pound, Scratch, Gust, etc. However, these moves only have a base power of 60, 50, and 40, decreasing respectively.
Wing Attack having 60 base power isn't terrible though, as Scizor and Scyther both have Technician, which will boost its base power to 90.
So in terms of PP and base power combined, I would go with Scizor. You can find Scizor by going to Route 21 in Pokemon X and Y and trading it, holding a metal coat so it evolves, to your ORAS game, or just hop on the GTS and search there. Here's a moveset I would recommend for a shiny hunting Scizor:
- False Swipe (Level-Up at Level 21/Move Relearner/TM)
- Metal Claw /Bullet Punch (Level-Up at Level 13/Move Relearner, Level-Up/Move Relearner)
- Wing Attack (Level-Up WITH SCYTHER at Level 21/Move Relearner)
- Roost (TM)
If you need an item, I would give it Scizor's mega stone or leftovers. You can run Bullet Punch over Metal Claw for priority if you want, but it has less base power and less PP. Along with Scizor's great defense stats and attack stat, its ability Technician multiplies a move's base power by 1.5 (if under 60), meaning:
-False Swipe now has a base power of 60.
-Metal Claw now has a base power of 75 (Bullet Punch would have 60 base power).
-Wing Attack now has a base power of 90.
-And roost is for keeping your health high.