The stainless steel ZapCap is an ingenious British invention that removes any crown cap via smartly-applied downward pressure. Hidden inside is a spring-loaded mechanism. Place the whole contraption over the bottle top and zap it down with the flat of the hand to lift off the cap in one action. It even magnetically retains the top for disposal later - though if you give it a rather over-zealous thwack the top can adopt a mind of its own.