As of Generation IX...
- 10,000,000 Volt Thunderbolt
- Aeroblast
- Air Cutter
- Aqua Cutter
- Attack Order
- Blaze Kick
- Crabhammer
- Cross Chop
- Cross Poison
- Dire Claw
- Drill Run
- Esper Wing
- Ivy Cudgel
- Karate Chop
- Leaf Blade
- Night Slash
- Poison Tail
- Psycho Cut
- Razor Leaf
- Razor Wind
- Shadow Blast
- Shadow Claw
- Sky Attack
- Slash
- Snipe Shot
- Spacial Rend
- Stone Edge
- Triple Arrows
Each move increase the critical hit ratio by one stage respectively (with the exception of 10,000,000 Volt Thunderbolt, increasing it by two), or two in Gen II. The probability of these attacks landing a crit is therefore 12.5% from Generation III onwards, 25% in Gen II, and 50% for 10,000,000 Volt Thunderbolt.
The held items Razor Claw and Scope Lens, as well as the ability Super Luck, raise the crit ratio by one stage each.
Source