as tight as a camels ar$eole in a sandstorm
mad as a box of frogs (my fave)
sorry folk this ones rude, for someone who's thirsty "as dry as a nuns ******" (add your own amount of stars for this one) lol
like a fart in a colander (for someone who isnt much use)
about as welcome as a fart in an astronauts suit
as rare as rocking horse sh1t
This is not quite the same but i like it anyway,my mum always says "oh well, every little helps, as the old woman said when she piddled in the sea"
i do apologise, mine are all pretty rude :-)