We see deals all the time on USB-A to USB-C cables, but discounts on C-to-C cables, which are necessary for faster Power Delivery charging (used by the new iPad Pros, the Nintendo Switch, and a bunch of laptops), are bafflingly rare. Today though, you can get an Anker PowerLine II C-to-C cable for just $7 with promo code ANKE8481, or double your length to 6' for $8 with promo code ANKE8482.
PowerLine II cables are incredibly durable, and also come with a lifetime warranty, so if you ever do wear it out, you can contact Anker for a free replacement.