If he really wanted a bizarre build, he could go for a warlock using a pair of pact blades, bard using song blades, or a sorcerer with paired daggers. None of them have two weapon attacks, but can benefit from dual implement spellcaster feat, and it flat out looks cool.

Even when the Fighter leans Striker, it doesn't come close to the Ranger's DPR, and the two weapon Barbarian is considered the weakest of the builds.