Hehe I always loved TAKE METAL in SQ3.
Some more funnies:
"Boo" in Mental Conflict

Putting your head in the hole in SQ1
Drinking the acid SQ1VGA
Any of them in SQ5
Entering the shower in The Colonel's Bequest
"You go now and I don't re-arrange your organs" SQ6
The stomach acid in SQ6
(I like Space Quest ;D)