Exactologist
An individual whom is concerned with the exact particulars of every topic being discussed. Will let third party know when they are incorrect about any and every topic, even if the topic in question is minor or unimportant.
Third Party: "Bill and me went to the lake to fish, and it must have been about late September"
Exactologist: "Actually your wrong it was September 15th, so more like mid September."
Exactologist: "Actually your wrong it was September 15th, so more like mid September."