annuals? what about sunflowers but they take some time to get there.
then you might consider sweat peas, morning glories, nasturtiums. I cant think of many more to be honest.

thanks seaburngirl

Sunflowers are what come to mind to me, also.

If you can provide a trellis, you could grow Eccremocarpus scaber up it, or Tropaeleum peregrinum (Canary creeper)

I grew nasturiums up a screen a couple of years ago, and they must have got to about 6 foot. Very easy to grow too.

thanks all

Some Amaranthus will make 6ft. Don't know the exact strains though.