Probably going to agree on the 512 head. It's a 512 item that makes you well, you! A head can really give you an identity in this game. It's really only sucky if you don't use it.
Alternatively, pure force. Looks nice on it's own, and if you get joints, the colour isn't altered like it would be with any other force. If you have pure force and full 128 joints, you technically have every single force available (because you can just put any colour onto your joints). Colors (the player) is the perfect example of this if you want to Dl/Lp him (he's wearing pure force/lax and has multicoloured joints).