Rook + Unclean Beast. Beast can Grapple giving rook an easy hammer slam, rook can bould roll to catch someone who is running. Both do good dps at melee.
Erebus + Regulus. A lot of the time regulus can be dealt with, if just barely, 1v1. Erebus with his bat swarm + 2 different snares (charm, bite) can quickly turn a 1v1 into a 2v1, into a 2v0.
Oak + Sedna: If both have priests, and are maxing out their main aggressive skills, they can be very hard to drive from a lane. Penitence + Pounce (Or, as I call it, Pouncitence) is a good deal of up front damage, and easily repeatible... even on a running enemy.