Oh. An old friend lent it to me. You know, he doesn't really ride a pale horse, but he does have 3 amigos.
Keep it. Dean's covered. Death's own. Kills.. golly, demons and angels and reapers and rumor has it... the very thing itself.
Crowley gives Dean the scythe before the two go to Chicago to find Death, telling him it is believed to be capable of killing Death himself. Armed with the scythe, Dean nervously tries to ambush Death in a Chicago pizzeria, but the handle begins to burn in Death's proximity and Dean drops it. Death thanks him for returning the scythe.