No Guard

No Guard causes all moves used by and against the Pokemon to bypass accuracy checks entirely, introduced in Generation IV. Both the user's attacks and incoming attacks are guaranteed to hit, creating a high-risk, high-reward dynamic where powerful but inaccurate moves become reliable at the cost of never being able to dodge anything.

The guaranteed hit effect extends to Pokemon during semi-invulnerable turns of moves like Dig, Fly, Dive, and Phantom Force -- a No Guard user can strike targets that are normally untargetable. One-hit KO moves (Sheer Cold, Fissure, etc.) are explicitly unaffected by No Guard and still use their normal accuracy. A notable Platinum-era glitch caused moves to have a (100 minus accuracy)% chance of hitting through Protect and Detect, though this was fixed in later generations. As an overworld effect, having a No Guard Pokemon in the lead slot doubles wild encounter rates.

No Guard is found on 8 Pokemon, with Machamp being its most iconic user. The combination of No Guard with Dynamic Punch (normally 50% accuracy, causes confusion) creates a 100% accurate confusing STAB move -- one of the most feared offensive tools in competitive play. Golurk and Honedge line also benefit significantly, using it to land otherwise unreliable moves like Stone Edge without ever missing.