I'm seeing a lot of people saying things in the comments about katanas and axes and morning stars and such. The thing about those kinds of weapons is that they take a while to draw. Looking at the gameplay that we've seen from E3 and various other videos, it looks like most of the melee weapons are on the belt or the shoulder and they all appear to be small knives. Now, the animation for the melee, while long for that sort of thing, isn't long enough to compensate for somebody drawing a katana, slicing the enemy to hell, then resheathing it. Granted, this is just one example based on what we've seen in the videos. I think that if we were to have any kind of customization in our melee weapons, it would be in different kinds of small blades. I've seen mention of butterfly knives in the comments; those might work. As might hatchets/tomahawks. Something that could be mounted on the shoulder or in a belt sheath that is small, quick to draw, and deadly. However, until Bungie either shows us more gameplay with other options on the animations, or we all get our grubby little hands on the game itself, it will remain a mystery. That being said, I think it would be pretty neat to have a kukri or tomahawk. It would be aesthetically pleasing I think with my Warlock garb. ^_^