I'm a bit phlegmy at the minute and a minute ago a I coughed up a huge mass of the stuff which then sat at the back of my mouth for a second before i washed it down with some water (i'm in the office, so hurling a greenie out's not really on the cards). Whilst it sat at the back of my mouth, i was close to retching and it thus inspired this thread.
Clearing up cat shit also makes me retch.
A mate of mine retches uncontrollably if you say the words 'maggots on poo' to her. Hours of fun.