I find the original 5 the most interesting personally but some of the Impel down lads also have a bit of uniqueness to them as well.
1. Lafitte - My personal fav, most mysterious and stands out to me the most outta the original 5. Initially setting in his Vivre Card was also intriguing.
2. Van Augur - From the moment he shot down that bird from fck knows how far with Usopp saying it wasn't humanely possible, I was sold. Plus he has a dope design and a sick epithet. Also like the fact the he's quite hot-headed as opposed to his cool demeanor.
3. Doc Q - Crazy mofo lol so pretty interesting. Sickly quirk is also pretty interesting. Has a dope nickname and an interesting fruit as well.
4. Burgess - Least interesting of the original 5. Quite literally a muscle head but the potential of his DF from a brute strength perspective is interesting.
5. Devon - Crescent Hunter epithet as well as the story behind it is pretty interesting. Fact that she isn't the typical hour glass beauty as is usually the case with One Piece women is also interesting. Plus her DF is pretty dope as well.
6. Pizarro - Not a fan at all. Think his DF is ass as well but he has personality to him. The Cat speak speech pattern is pretty interesting but given his DF nothing might come of it. His backstory is also interesting. Don't like his character type though. Interesting nonetheless.
7. Shiryu - Character-wise he isn't really that intriguing to me but fact that he seems to have no honor will make for an interesting contrast as Zoro's opponent. Also curious as to why he chose Abaslom's fruit and lowkey looking forward to how he applies it. Also hoping for some potential Wano Law with him.
8. Wolf - A Low IQ simpleton isn't necessarily a bad character type. Reckon his backstory could be interesting but don't got much to say about him apart from that.
9 Vasco - No Comment lol. Fighting style could be interesting if his alcohol has a similar effect on him as it does Kaido but just know that Oda's not gonna deliver on that. Will prolly be some flame spitting fuckery instead