John McCain will run for reelection in 2016 and his fate will depend of whether he has a strong primary challenge from the right. If he makes it through the primary without many bruises, he will cruse to a reasonably easy reelection. If this becomes an open seat or the incumbent is irreparably damaged in the primary: this could be come interesting. Don't hold your breath here.
It is always worth giving a look to Arizona's 1st, 2nd, and 9th Congressional Districts. These are quite "swingy" districts. If Clinton does reasonably well is Arizona, these three seats will likely be held by three Democrats.