Elyan: Can you two please try and see things from my perspective?
Gwaine: *crouches*
Percival: *gets down on his knees*
Elyan: I will duel you both.
I would bet that at one point, probably S1-2, Arthur tries to teach Merlin how to use a dagger and then immediately regrets his entire existence.
Think about it. He has a manservant who is bound and bloody determined to follow him literally everywhere, sometimes literally into the jaws of malevolent creatures, without armour or weapons or even basic survival skills, it seems. Of course, Merlin is more likely to injure himself than anyone else with a sword, so Arthur decides to give him a dagger instead. He was given his first dagger when he was seven. Merlin should be able to handle that, right? A dagger is small enough to be carried around without general suspicion, it’s not heavy enough for balance to be an issue (of course, with Merlin, balance is always an issue) and it doesn’t really require the skill a sword does. Hold the dull end, stick the pointy end in whoever is trying to stick you. It isn’t like Merlin isn’t ever in the thick of a melee anyways, so hopefully he’ll never need much skill.
At first, it almost seems like a good idea. Arthur gives Merlin his very own blade (it was Arthur’s, years ago, so it’s far better than whatever kitchen knife peasants normally use) and it takes, oh, about three days for him to realise that he’s made a terrible mistake when a guard comes and tells him that Merlin almost shanked someone in the tavern and started a brawl that sent three people to see healers. According to Merlin, his almost-victim had been talking unfavourably about Arthur. When he refused to shut his trap, Merlin decided to shut it for him. At dagger-point. He doesn’t know if he should be flattered or horrified than Merlin is willing to bleed someone just because they were speaking ill of Arthur.
This becomes a Thing.
Arthur has Regrets.
Arthur, trying to wrest the dagger out of Merlin’s hands: Let – let go. You can have it back when you learn some self-control. Daggers are for good servants who don’t assault people at random.
Merlin, keeping a death-grip on the hilt and glaring at the drunk who’d compared Arthur to the King: It isn’t random.
Gaius: I told you to look after merlin.
Lancelot: He'll be fine. He's a sorcerer.
Gaius: That's just what they're called. It doesn't mean he actually knows what he's doing.
Gwen: Will you look after Arthur?
Lancelot: He'll be fine. He's the King of Camelot.
Gwen: That's just what he's called. It doesn't mean he actually knows what he's doing.