I've experienced balls deep down the throat once or twice, it felt phenomenal on my cock. But not tried the laying back, throat fucking as per the picture above. I'd quite like to try that with the slobbering choking thing, obviously with a lady who enjoys it.
I'd even go as far as a Roman Shower with the right lady, just to tick it off the list.
I did have a lady gag on my cock a bit recently, but I was barely in her mouth. She did say that she has a very sensitive gag reflex though and doesn't much like the retching sensation.