Given your circumstances, I don't know that you need one. If you die (heaven forbid) intestate, your state will have rules in place about how your effects will be disbursed; you can check what those are -- likely next of kin, your parents and/or siblings -- and see if you're OK with that. In my state, a hand-written will (I don't think it has to be witnessed, even) is enough. Be aware that (again, in my state, but I think pretty typical) regardless of whether it's the hand-written or the more formal kind, it must be the original, not a copy, that is presented if one is needed (heaven forbid).
(Full disclosure: I do have a will, but I'm at a very different life stage and have a dependent. To take another example, though, my dad, in contrast, doesn't have a will, and as he has basically no assets and would in any case write a will that would mirror the state's rules about dying intestate, I don't worry about that. Not everyone needs a will.)