Aquion Pro Dry Suit in the UK - very reliable and easy to repair. Easy to get on and off as well.
5 mm one piece wet suit for warmer waters although often jsut dive in polo shirt and a pair of cotton tartan "play pants" where it is too warm for 5 mm. Just gives you that bit of protection against stingy things in the water.
<font color='#000080'>Seriously, a Northern Diver Vortex membrane drysuit for the UK.
For warmer water I have a 3mm Typhoon wetsuit which I combine with a selection of Reed Chillcheater undergarments to suit the water temperature (or even the Chillcheaters on their own). I've also got a 5mm Beaver shortie, but that's never seen use outside a pool.