So you make two major questions here. First, what specs can you make? Second, how can you make it different from the Rogue? I can do both right here off the top of my head.
Demonic Fury - Melee DPS Spec - Specializes in dual wielding and aggressive attacks. Plays a lot like the fury warrior (use a rage-like mechanic) but with more utility (like a rogue). This is your traditional glaive-wielding Demon Hunter.
Dark Ranger - Ranged DPS Spec - Finally a spec other than Hunters that uses ranged weapons. Plays a lot like the Diablo 3 Demon Hunter (people /do/ like it). But instead of traps, they use curses (almost like affliction). It sits about midway-leaning-SPriest between SPriest and Warlock on the DoT VS Direct Damage scale.
Transfiguration - Tanking Spec - This is the spec you've all been waiting for, this is the metamorphasis spec. It has a lot of AoE abilities (aura-style, not place and forget style). Designed around using 2h weapons for powerful, but infrequent, attacks. This is a traditional "eat the damage" spec that makes up for not having a shield by having an increased chance to dodge.
The only spec I mentioned with any relation to rogue was Demonic Fury, which suffers from the fact melee is generally very boring.