Rin can go into battle with a kitchen knife.
One notable occasion revolving around this was in which someone broke into his and Yukio’s dorm in an attempt to kill him (”THIS IS THE THIRD ASSASSINATION ATTEMPT THIS WEEK!”) and Rin, armed with only a cheese knife, cut the hell out of the lady who was tryna kill him and threw her out of the 3rd floor window….several times. Like, he went outside, picked up her body, walked up the stairs, and threw her outside of the window again before rinsing and repeating.
Mind you, the entire time he was sick with a 102.7F (39.3C) fever, wearing Spongebob boxers and a Deadpool shirt that was inside-out with one taco sock. Like, he was just wearing one sock. And then he passed out after his fever hit 103.9F (39.9C) and Yukio took him to the hospital.