Actually, few Celts fought naked at the time of Hannibal; mainly the cultic mercenaries called the 'Gaesatae'; they carried javelins and a sword and shield (they were highly favored for their fanatic nature, ignorance of pain, and fearlessness, attributed to a PCP-like drug they imbibed before battle). Naked warriors had fallen out of any major favor around the turn of the century, in Gaul. However, the Galatians, during their migration, had missed that cultural shift, and did have large numbers of naked warriors (but it still didn't form a bulk of their military by any means, but they weren't so rare it'd be surprising to see one). Anyway, I should point out though, the sword was the main melee weapon of many Celtic and other cultures warriors. A sword is light, a glancing blow with it can still some one, it can be manuevered in different ways than a spear, it's accurate, easy to get the basics of (but can take years to master the usage of it), and resilient. Spears broke all the time (as did many shortswords, which were often little more than very long hunting and skinning knives); a sword could, if properly cared for, last generations, and was an investment. A spear can also be awkward in many situations, they require the body to move in sometimes unusual ways. Swinging a sword is a very natural series of motions. They both have their uses, and advantages, but not everyone used the sword as a back up. For instance, like later sword and buckler troops, some Celts used a small round shield and a short stabbing sword; they were anti-phalanx light infantry. They'd knock the spears up, roll underneath, and stab the spear/pikemen; the Pergamons started kneeling a few rows of their pikemen to stop this (sadly, we can't actually do either of these things in game). The Galatians were huge on using this tactic, because, of course, they were mostly fighting troops from Sucessor states, and an anti-phalanx troop was highly valued. Anyway, the sword was their main weapon. Also, Romans shifted to somewhat hardier, slightly reinforced shields, because the veteran Gallic soldiers had well made longswords (as their main weapon, at that), which could often break their shields (similar to the Dacian falx causing a complete adaptation of Roman arms and armor). Romans mention Celtic swords that bent and broke easily, but many times they're talking about shortswords, which aren't really made for combat much of the time, but were used by younger warriors who needed a weapon. Many Celtic swordsmen (most, even) carried javelins, but their main melee weapon was still a sword.