This addon is intended to help you remember which NPC drops which unique item. As you mouse over an NPC, an additional tooltip for the item is shown. Timeless Isle rares often have secondary drops as well, shown in a shortened secondary tooltip.
By default, tooltips fade after being shown, unless the item is still required for an achievement. Holding Shift keeps them shown. Options are on the way! (I just suck at XML)
There is data for the mentioned 5.0 and 5.4 rares, Zandalari Warbringers (to help identify which mount they can drop) and some other NPCs, mostly from Pandaria, that drop interesting items.
I'm very open to suggestions what else could be added (Draenor rares are on my to-do list)
r03: Patch 6.0 compatibility, secondary tooltips for secondary drops, auto-fade
r02: removed functionality to equalize the widths of unit tooltip and RaresTip frame. Sorry for that. Didn't work when I tried it on my end, so I forgot about that code, and people disliked it.
r01: initial version. Still has the tooltip "bug" mentioned above, if you like it. May or may not actually work.