Mad Maniac with axe-firing chainsaw said:
I'm gonna have to go with the francisca, with the gladius as my back-up weapon.
The francisca was carried by the Franks, and was thrown. The value of this over more traditional thrown weapons was terror. The axe path was so unpredictable that it was almost impossible to avoid or block, and was very heavy, so shields and armour were next to useless. As such it made an excellent morale breaker before battle was joined. Aside from its thrown value, like all axes the francisca makes an excellent melee weapon, and is actually superior to a sword of the same length when both fighters are heavily armoured. (It is much more likely to pierce and can still be used to parry.)
Gladius. Nope, not a gladiator weapon exclusively. The gladius was your standard Roman sword. Its not very effective as a stand-alone weapon. Where it really came into its own was in large formations. In battles, two armies can get locked so tightly together that its impossible to swing a longsword. Combined with the large Roman tower shield, the only piece of equipment of their own invention, a short stabbing sword in these circumstances is perfect, and one of the main advantages the Romans could bring to bear over the Gauls. Bear in mind that the Romans did not use this sword till the end of the first punic war. They adopted the design off the Spanish, who used them first. They also got the idea for pilae off of the same people. Before that, Rome used the Greek sword, another borrowed design. The reason I would want this as my reserve weapon is because its light and handy, and short weapons are harder to parry than longer ones.
EDIT: I'm not sure if they did pinch the design off the spanish. I'll check that now.
2nd EDIT: Hey, I was right! I didn't want any of the other weapons. Either too unwieldy, or, like the sword-breaker, way too prone to breakage itself.
I'll give you the franchesca. It doesn't matter how much skill it's thrown with or how the weapon lands, it's got enough mass to do substantial damage regardless.
However, though it becomes increasingly difficult to parry as weapon sizes get smaller (especially when it's a thrusting weapon) the difficulty doesn't increase as rapidly as you imagine. Even though a gladius is only 1/3 the length of a standard medieval rapier, you'll find that you actually have the same space of time in which to parry the blade (for someone like me, this equates to a distance of about 8 inches in which to successfully parry within (for a thrust to the torso), arm length is primarily what's going to affect the space in which you can parry a thrust). The only thing that makes it more difficult is a simple matter of physics - a shorter sword is a shorter lever arm meaning it requires progressively more strength to parry. Even though I only weight 145lbs, I could easily parry the thrust of a 400lb world champion weightlifter because of the absurd advantage in leverage you have with a proper parry (this is with respect to fencing with a foil, which is about 36 inches long, the principle remains the same with any thrusting weapon). On the other hand, if one is fighting with knives (even fairly large ones) the leverage advantage I have over the other person is minimal and as such a parry is nearly impossible because of the difficulty involved in applying enough force to significantly redirect the blade (in this case you're better off trying to redirect the opponents arm instead).
In the same vein, a sword becomes increasingly effective on the offense as size increases, up to a point. Once a weapon weighs more than 2 - 3 lbs your options with the blade are whittled away because of the difficulty involved in in some actions. Modern fencing stresses the idea of duo tempo fencing, wherein a parry and a reposte are separate and distinct actions. With a true rapier, such an action is nearly impossible because of the mass of the weapon. In this case you must resort to stesso tempo, where a parry and reposte become the same action. Because of this very reason, during the age of the rapier (what most people think of as a rapier is actually a court sword, which was fully two feet shorter than a rapier) people generally carried a second item specifically for defense (from a cloak or buckler to a very long dagger), and the circular nature of combat and deliberate pace dictated by the weapons means combat is relatively slow and plodding, becoming a game of angles more than anything.
As such, I'd place a court sword or a dueling epee as a far superior weapon when against a foe with a gladius (assuming no armor is involved). The weapon is lighter and longer meaning your foe is placed in a precarious position where they are often going to be forced to react to your actions rather than dictating the pace of combat themselves. Assuming we were going to opt for period pieces here, there were only two schools of thought for either weapon - French and Italian. The French style (which has a slight curve and angle to the grip) emphasized finesse but was difficult to apply significant force with (and was relatively easy to remove from the hand with an expulsion maneuver). The Italian style (which has a straight grip and a cross bar that you hook your index and middle fingers over) allowed for greater application of force (and was more difficult to remove from the hand). Personally, I favor the french style myself (though in real life fencing I use a Viscontii grip, which actually resembles the grip of a gun).
If we are discussing foes with armor (as the poll implies), my vote goes to the bill hook - one of the most brutally effective extreme close quarters anti-armor weapon. Essentially, a bill hook was a short weaponized pick axe. The mass of the weapon and it's fine point meant that it could outright punch through most types of armor, and the irregular nature of the blade (and it's curve) means one could simply yank entire pieces of armor out of place.
For something a bit simpler, I've always been a fan of the flanged mace.
