A list I've seen before somewhere else, so it might all be a bit of leg-pull, but fun nonetheless. Allegedly the cream of the crop of bad metaphor writing from the UK's GCSE English exam paper. There's many classics in there, but my faves would have to be...
"She was as easy as the Daily Star crossword."
"Long separated by cruel fate, the star-crossed lovers raced across the grassy field toward each other like two freight trains, one having left York at 6:36 p.m. travelling at 55mph, the other from Peterborough at 4:19 p.m. at a speed of 35mph."
"The little boat gently drifted across the pond exactly the way a bowling ball wouldn't." [Total Hitchhiker's Guide to the Universe steal, that one