95% Metaphors add to list

Some items are used as metaphors so often that they can hardly be taken seriously in their true sense any more. For example, people don't take me literally when I say, "My nephew's major in college was rocket science." They look for some allusion when I say, "Ben Franklin established milestones along Rt. 9 in Massachusetts." It's too bad when we can no longer refer to an item as itself. What do you say when you really do have a thorn in your side? Here's a list of words which, for the most part, have lost their original meaning and become 95% metaphors.

rocket science
milestone
guinea pig
bootstrap
red herring
brain surgeon
lame duck
black sheep
dark horse
one-armed paper hanger
hardball
tinker's dam*
Watergate
Waterloo
square peg
pain in the neck
tough cookie
fine-toothed comb
fine print
thorn in the side
wallflower (cerinthus)
pigeonhole
slippery slope
line in the sand
soft soap
chopped liver
bread crumbs

*Tinker's dam, a wall of dough raised around a place which a tinker (itinerant mender of metal household utensils) desires to flood with a coat of solder. The material can be but once used; being consequently thrown away as worthless, it has passed into a proverb, usually involving the wrong spelling of the otherwise innocent word ‘dam’.