Today I wrestled a jar of Old El Paso guacamole for 5 minutes, using the strap wrench Kim suggested a few years ago, before it finally ceded with a gratifying pop. (Taste and texture were vile; no more than deserved for not making it myself, but that's beside the point.)
As I'm pushing my knuckles back into the right places MrsT says "here, have another go" and passes me a jar of OEP salsa roja (which tastes OK because we don't know any better). I get the lid lassoed with the strap wrench, dampen my left hand to give it a grip, and wrench away. Jar rotates in age-enfeebled grip. I set it on its side on the chopping-board, grip again and lean on it into the bargain.
Wrench.
Pop.
Rattle.
Ever had to scrape up half a jar of salsa roja from your chopping-board?