Writers often use "pun" when they mean metaphor, "metaphor" for any figure of speech, and "grammar" for correct English.
With a mayor who has put an onus on cycling provision… (BBC News 2013-08-12): emphasis – an onus is a burden
Honours system is outdated, rooted in our colonial past, often politically corrupt, usually rewarding those who have more than enough already. (Irene Short/@ipasho) What do honours have to do with colonialism?
that doughy-eyed look: it’s “doe-eyed”, like Bambi
Winnowing Down Religious Liberty: Whittling reduces gradually, winnowing gets rid of the bits you don’t want.
sacrableur! Sacré bleu!
Lady X came from an old country family: County family. “The County” were the big landowners of a particular county. They sometimes, but not always, had hereditary titles. They were listed in Burke’s Landed Gentry. “Landed gentry is a largely historical British social class, consisting of land owners who could live entirely off rental income.” (Wikipedia)
ripe with disease: rife
hermetic for hermitic (“He had become increasingly hermetic.” Julian Barnes)
fervent name-guessing (BBC, July 2013): fervid (feverish, not religious)
intervene for intercede
obstruse for abstruse (confusion with obtuse, obscure, oblique)
pilfer for plunder
lest for unless (it means “for fear that”)
asterix for asterisk
inconstant for inconsistent: The company has produced inconstant maps for the players as to what parts are still free to play on. (New Statesman Aug 2013)
More here, with links to the rest.