I'd I look at them with a non-realistic face. And I would reply " Isn't it amazing! C:" And then I'd look at them again and say "Wow really? 당신 figured that all 의해 yourself sherlock? Nothing gets past you."
My best 프렌즈 tell me this on a regular basis, and I say it myself, so I usually say, "Yeah I know." Even if an enemy says it, I usually say, "Yeah I know. And..loving it." I am a little strange, so I'm used to people thinking so. They're usually right. :)
Depends whos saying it. If it's my 프렌즈 in a joking way, I'd be like 'Yush, I know I am! And it's good to be weird, 당신 should try it,' but if someone is actually meaning it I'd be like 'Well, 당신 are too but I never complain about it,' XD
I would tell him/her that I know I'm weird, that I'm proud of it, and then start spouting enough weird facts about myself until the person regrets calling me that. But I seriously so agree that I'm weird. I've got a 스플릿, 분할 personality, ADHD and awkward obsessions with many 아니메 characters. XDXDXDXDXDXDXDXD