Formal:
* "Bagay na nakakainis" - This literally means "thing that annoys" and is a good general translation.
* "Pantanging inis" - This literally means "special annoyance" and highlights the personal nature of a pet peeve.
Informal:
* "Kaka-asar" - This is a colloquial expression meaning "annoying" and is often used for something that makes you irritated.
* "Nakakairita" - Similar to "kaka-asar," this also means "irritating."
* "Nakakapikon" - This is a more slangy term for "annoying" and can be used for things that really bug you.
Examples:
* "Ang kaka-asar ko sa mga taong nagkukuwentuhan ng malakas sa bus." (I find it annoying when people talk loudly on the bus.)
* "Ang pantanging inis ko sa mga taong naglalakad nang dahan-dahan sa escalator." (My pet peeve is people who walk slowly on the escalator.)
The best translation will depend on the specific situation and the level of formality you're aiming for.