The person may change depending on the situation.
If you are in the sales process it is important to identify who has the final say in the purchasing decision and ideally get him/her onboard with what you are proposing. Depending on the sale the person may change, so how can you identify the key player? I read a sales tip published by Miller Heiman that identifies 4 variables that may affect who controls the purse strings. Read the article, "Find The Floating Decision Maker".
(Note: This article expires, if you are interested read it soon!)
Happy Friday and have a wonderful weekend!
-Brianna