The only time anyone should use L/K rings are if you don't have Rajas. And if that's the case, you best drop whichever ring you do have because Rajas is miles ahead of any other CoP ring.
The new Spiral Ring is very nice for MNKs since it has +5 to both STR and VIT. A great Tornado Kick ring. Vulcan's Ring is slightly better for TPing and if you can get people to do Tier 3 VNMs, Strigoi Ring is even better.
I suppose Zilant Ring is also worth mentioning but it's not as good for 1 hander's acc as Toredor's or Sniper's +1. Better than NQ Sniper's though.