If money would allow, I'd love to cosplay Korosensei. He is one of my favorite anime characters of all time and is a character that I look up to.
You can buy a costume for him, but it is $129, plus $50 shipping. I actually got enough to buy him but decided to get a wig for Armin instead. No the wig was not that expensive, but it was enough that I couldn't afford the cosplay.
I hope to be able to cosplay him one day.