Newegg offers the Western Digital 4TB Elements USB 3.0 External Hard Drive, model no. WDBWLG0040HBK-NESN, for $129.99. Coupon code "EMCWHHD42" cuts it to $119.99. (B&H Photo Video charges the same.) With free shipping, that's the lowest total price we could find by $12, although we saw it for $3 less two weeks ago. It features a data transfer rate of up to 5GB/s. Deal ends January 1.
If you haven't yet, use coupon code "MBLMASTER15" and pay via MasterPass using Newegg's mobile site to cut it to $114.99. (This discount can only be used once per account and doesn't stack with the above coupon.)