Still pretty new to cigars but still haven't had anything that I would say put me on my ass. LFD Colorado Oscuro was close and maybe the Fausto. Don't think I get affected by nicotine as much as some people. I'm the same way with caffeine.
I was a lot like you at one time. For the first few years of this hobby, there wasn't a cigar made that could put me down. I would laugh at the latest, greatest, power bomb. Nothing could touch me. All of a sudden, my favorite cigars started turning me green less then half way through. For several months, I couldn't handle anything but mild to mild mediums with cammie or connie wrappers.
The sensitivity to nicotine left about as quickly as it had come. I'm to the point now where I'm almost back to where I was, although there are still a tiny handful of smokes that can make me green.
Weird thing is that I developed a caffeine allergy, right around the time I was having problems handling nicotine.