Good antonym for "pet peeve"
Solution 1:
What about a penchant, or even, if you wanted to alliterate, pet or personal penchant?
(UK): /ˈpɑːnʃɑn/, [ˈpɑ̃ʃɑ̃]
(US): /ˈpɛnt͡ʃənt/a taste, liking, or inclination (for)
He has a penchant for fine wine.
Solution 2:
How about soft spot?
From Merriam-Webster:
soft spot: a strong liking for someone or something
Given that a pet peeve is something that annoys or bothers a person very much, i.e., is something one dislikes strongly, it would seem that soft spot is an appropriate antonym.