Newegg offers the refurbished Cooler Master CPU Fan, model no. DP6-9EDSA-0L-GP, for $7. Redeem this $7 mail-in rebate to cut that to $0. With $1.99 for shipping, that's $10 under the lowest total price we could find for a new one. It's compatible with Intel LGA 1150/1155/1156. Deal ends August 4.
A 90-day warranty applies, although it's unclear who backs it.