Cost effective wise: taskestos, teceitos, bastarnae, thraikikoi peltastai, and sloxonez. High lethality, ap, and capable to murder everyone in short time. The ultimate one was gaesatae, i once had one half depleted unit of them eat halfstack of hastati and haploi on walls. If you are capable to got naked dudes with swords, you should definitely used em on walls.