Good rings to use in PVP?

Apart from the obvious ones (FaP, Havels, Wolf, RTS DWEG, Leo and Hornet) are there any other useful ring for pvp?

Well if a ring is considered good (which most people with a fair amount of Dark Souls experience can tell which are and which are not), and the ring is what you want for your character, then its good.

However, you happened to name mostly physical rings, bellowing dragon crest, not bad for some people, lingering for others, I use Ring of Fog (only after nerf humorously) to protect me from other mage's pusuer and soul orb spells. I'm kinda surprised I don't see it more.

I also love the Clortanthy Ring, so good in my opinion, although Grass Crest is already a very solid shield, and if you add that green grass...

favor and wolf wing is one of the best combos for dex cause it means you can swap to rtsr when in low vit, imo you don't really need any other rings. for str havel's since str weapons are so damn heavy(im talking about the big ones) and wolf so you can swap wolf too, yeah you can go favor but with favor ring you'll have a lot les choices for armor, if any. yeah you can use favor and havel'ss together but I personally like swapping rings, it has saved my behind so many times.

If you already have desired poise and roll, you can always go with a ring which raises your defenses.

Ring of Steel Protection ain't horrible at really, REALLY low level pvp.

Some of the "attunement slot" rings can be useful for people trying to get that 1 extra slot.

Other than that, everyone else pretty much nailed it.