Man, I have so many for this topic, where to start...
I probably couldnt list all of them off the top of my head, but
One of the earliest ones I had, which is about to happen soon anyway is Achilles my Gunpowder character interacting with Foxrally's character Sophia. For starters the rich northern background of the two will make their conflicting views on the barren lands really interesting.
Another is my original Venice character Lorenzo, who I would've loved to see interacting with Ice's rather unassuming, but still dangerous Vampire Arabella.
Finally one of the ones I most want to see(Besides my dust character and pretty much everyone bigger than him) is my Venice character. Since she's easily one of the weakest in the RP, both in status, finance and abilities I'd like to see her taken under the wing of one of the more powerful family heads in the RP. A few of the ones I'd think would particularly suit her are Wooliest steams character, who like her is human and would be able to relate on a personal level since they're both orphans who's parents were killed by monsters(Although unlike him, she doesnt know how they died). Anivia's character would be a good fit, since my character's ignorance to the existence of monsters would make her see him as rather unassuming, while in reality he could easily manipulate her as a vampire and eventually into becoming one. It would also fit since they're already connected in some way in that she frequently visits one of his families brothels (Although they've never met). The final one I see being a great fit is under score's character. The fact that she isnt in any way a blood relative of the family she works for would be perfect since my character would also have to gain the acceptance of the family through hard work as opposed to being welcomed due to being in a relationship with a member who is in through blood connection.