Most Midevil long swords or bastard swords could be gripped by two hands so I believe there where knights that could wield a sword and fight with both hands.
haha FTW...I have a T shirt with a "Hello my name is" sticker on it with the rest filled in with the Inigo Montoya line
Musashi was known to use a katana in each hand so that's 1 swordsman who was ambidextrous so I don't see why there weren't many who used 2 swords equally well or switched for certain situations like fighting the rare left handed devils
I doubt it, the word for left handed was sinistre in French or something like it, (if I'm not mistaken), because left handed jousters were more likely to fatally wound their opponent due to the positioning of the lance (on the side of the body, not the shield) So there was some superstition about left handedness. Also, an ambidextrous swordsman would likely have to have been self taught, as swords trainers I would assume would be like handwriting teachers twenty years ago, encouraging right handedness.
I'm sure there would have been some prodigies through the years who could use both hands, but it would have been rare.
Look up Daishō, it's the traditional pairing of a long sword (Dai) with a smaller blade (shō).
A skilled swordsman would utilize his/her weapon like it was an extension of their body. So yes, being ambidextrous is possible in my opinion.
Now try to be ambidextrous with a rifle. It's not a matter of how it feels in your hand. It's a matter of how your eyes work when aiming. Everybody has one eye that can see straighter than the other.
A good way to 'zero the dope' on your eyesight is to hold both hands together in front of you and form a pyramid with your fingers so you can look through it like a scope. Focus on something then close the left eye. Now do the same with the other eye. Whichever eye shifts the 'target' less is your shooting eye. If your shooting eye is left, you are a right handed shooter. If your shooting eye is right, you are a left handed shooter.
[DISCLAIMER] I am no weapons expert.
I'm not a gun guy but I'm perplexed by your post, why would the right eye not be the shooting eye for a right hander if thats the eye that looks down the sights? If your right is on the trigger then your right eye is above the barrel.
The German longsword traditions that come down from Liechtenauer have usage of either hand built into them at a fundamental level. Fighters were encouraged to begin with whatever hand was dominant, but in the flow of combat had to be able to cope with situations where they would need to use their other hand. They therefore trained both ways equally so as not to leave their opponents an exploitable weakness.
Also, with sword and shield combat, the shield is not a passive defense, but is used just as actively, if not moreso, than the sword. So that style of combat is inherently ambidextrous.
EDIT: So, no, there was no special title for this, as it was very common.
You are right. I should of mentioned with what type of rifles. If the rifle discharges shells (say like an AR-15 for example) then you'll need an opposite handed weapon so hot shells don't dispose on your skin. (if that makes sense)
Eye dominance. For most people, the dominant eye is on the same side as the dominant hand, but every now and then you have people who have their dominant eye opposite of the dominant eye. Because correct form with most sights is to shoot with both eyes open, if you are aiming with your non-dominant eye the super-positioning/occlusion of the sight gets all jacked up. Thus, even if you are right handed, if you are left eye dominant you shoot lefty; you can learn to shoot opposite of your handedness, but you can't change the nature of your eye dominance.