My loved one and I have all sorts of private pet-names but mostly they stay firmly private. The only one I would use publicly is the essentially descriptive “sweetheart” and even then only in a sympathetic gathering.
You can speculate furiously but my lips are sealed over the others. At least we like them all, unlike some pet-names that one partner or the other hates with a vengeance and tolerates with gritted teeth.
The most loathed term among women is supposedly babe or baby, closely followed by baby girl, baby doll, pudding and pumpkin. As for terms like sweetcheeks, snookums and muffin, I can’t imagine who could actually use them with a straight face.
Then there’s the question of how you refer to your loved one in the first place. Personally we loathe the words husband and wife and the negative associations they still carry, so they’re used strictly as a standing joke. We prefer partner, but some people dislike the corporate overtones.
“This is my man/woman” is apparently common in Scotland and Italy. “Lover” was modish at one time but seems to have lost favour. “Boyfriend” and “girlfriend” are still popular though strangely innocent-sounding in an age of sexual licence. “Spouse” is horribly formal and somehow vaguely insulting. “Cohabitee” sounds oddly clinical. One of my blogmates refers to her Significant Other.
Or you can just be super-subtle and say “This is Natalie” or “This is Damien” , leaving the assembled company to investigate the exact nature of the relationship for themselves.
As for extra-marital couplings, let’s not even go there. Though I always had a secret hankering to refer casually to my concubine. And watch people’s faces.