The Wall-Mounted Spirit Measure, as used in many a public house across the UK. Easily fixed to any shelf, or any wall once you've drilled suitable holes for the provided screws, the spring-loaded mechanism will grip almost all regularly sized bottles of booze. The litre-and-a-half vats of kiwi fruit schnapps that go for 1200 pesetas in Spanish island airports may not fit, but most things will.
The single greatest achievement of the Wall-Mounted Spirit Measure is to provide the correct amount of spirit for cocktails and mixed drinks. It's worth the wait of a few seconds to get accurate measures of your chosen tipple so that your drinks don't taste odd. Too much booze and it's easy to end up sipping on something that tastes as if it has been laced with nail varnish remover; too little and guests will wonder why you've added the alcohol to their glass using a pipette. With a Wall-Mounted Spirit Measure you're guaranteed no shoddy shot shizes.
Brilliant at parties - drinks are readily accessible, you don't have to walk around being waiter and no one walks off with two-thirds full bottle for selfish solitary consumption - the Spirit Measure is also a little bit of lounge lizard luxury in an otherwise hectic life. Feet up after a hard day, a hearty dash of something on the rocks. And you don't even have to lift the bottle. Marvellous.