Picking a few amusing ones from Portuguese and Italian that I use often.

• [PT] um polaco de cada colônia (a Pole from each colony): assortment of random items or people that might look related but aren't.
• [PT] o que o cu tem a ver com as calças? (what does the arse/arsehole have to do with the pants?): how is this shit even related [to something else implicit by context]?
• [PT] vir com o milho enquanto alguém já comeu a polenta (to bring the maize while someone already ate the polenta) - to think about something after someone else already handled it
• [IT] dire pane al pane e vino al vino (say "bread" for the bread and "wine" for the wine) - let's speak clearly, OK? No [eu/dys]phemism, let's call things by what they are.
• [IT] scoprire l'acqua calda (to discover hot water) - it's a bit like English "to reinvent the wheel": everybody already knew it, but you just realised it.
• [IT] l'ospite è come il pesce / [PT] a visita é como o peixe (guest is like fish) - don't overdo your stay; guests and fish, both stink on the third day.
• [IT] non avere peli sulla lingua / [PT] não ter pelos na língua (to not have hair on the tongue) - someone who speaks openly, not holding back

There's also a funny Latin insult that I tend to jokingly use translated fairly often, "funge putride" (you rotten mushroom). I like it because it's really light, not something to really insult someone.