There's Ryder (Wicked Obsession) who used it in front of Langley and she told him she didn't like it directed at her. He then made a concerted effort to not drop the F Bomb, but he wasn't always entirely successful.
Finn (Wicked Intention) uses the F Word around his teammates, but only uses it with Zo in two circumstances. The first is when he's angry. Finn's really good at appearing calm even when he's furious, so Zo's tip off that he's mad is when he uses her full name and/or uses that word in front of her.
The second scenario where he uses it with her is sexual. Finn and Zo have three modes: Making love, having sex, and f**king. I saw a scene between the two of them that didn't make their book and defined what they meant by these three uses. Unlike Langley, Zo doesn't mind Finn using this word in front of her.
Right now, I'm writing Griff's story, Wicked Salvation, and he has no problem dropping the F word in front of his heroine. In fact, he did it during the first conversation the two of them ever had. It doesn't faze Cat in the least. She used it right back at him.
He puts her back up and Cat doesn't back down. This is both good and bad. Good because Griff needs someone to push back when he's abrasive, but she's also impulsive and hellbent on her plans. She's already making Griff climb the walls. I'm enjoying this because he totally deserves it.
