Come up with a new ability, move, or item and then tell us what kind of effect it would have on the game.
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Example:

New Ability
Safe Entry ^{name pending}
Pokemon receives the benefits of the move Protect upon switching into battle.

This only applies during the actual switching turn. So say you have a Bisharp out and your opponent has a Terrakion out. Naturally, you'd want to switch. So you switch to your Safe Entry Pokemon and it takes no damage from whatever attack Terrakion used. Safe Entry also protects from status moves like Taunt, Toxic, Defog, etc. Basically, if it's blocked by Protect, it's blocked by Safe Entry. Therefore, anything that hits through Protect like Feint or Phantom Force will also hit through Safe Entry. Mold Breaker will hit through Safe Entry as well.

Safe Entry will share the same mechanics as Protect, including the mechanics for using it in a row. So if you have two Safe Entry Pokemon and keep switching between them, it will act the same as if you had a Pokemon just spamming Protect over and over again. If you switch a Safe Entry Pokemon in and then use the move Protect with that Pokemon, it will act like you're trying to use Protect a second time in a row and do what it does now in that situation with the 50/50 chance.

I think this would be an excellent ability to put on a frail but fast Pokemon, specifically one with either U-turn or Volt Switch. This guarantees it can get in without being hurt and then get out again for a bulkier Pokemon to absorb the blow.