For casters, i would like Ring of Bless. The +1d4 attack will help in not wasting spell slots when casting Chaos Bolt or Scorching Ray.Depends on the PC. Haste is awesome for most martial types and monks, not as much for casters or even rogues. For casters, ring of blur. However, a cloak of displacement pretty much already does the same thing and it already exists. If that matters.