Obsidian statues are defiantely worth keeping... some are desirable more than others for filling names in their collections but each one takes 10 rounds of a quest to do (requiring 10 obsidian pieces).
Rare names are - i think - ones which have love/truth/courage in their name (i totally forgot off the top of my head, but they seem to be very elusive).
As for the globes, rarer names are the Twin Oaks Tavern, Shrine of Chaos and blackthorne's castle (I think the name is). Super super rare is Exodus' Lair.