Completely trasparant glass is my favourite, I like to be able to see my lovely smoke.

I've got a 2 foot translucent darkish red acrylic bong with a glass on glass slide which is a nice bong indeed, but it'd be 100 times better if it was completely clear.

This is one i made outta a glass salad cream bottle - i already had the metal bowl/stem from the red acrylic one [i changed it to glass on glass myself, much better hits]

It's more like a bubbler coz it's pretty small - not for big big hits, but it'll still have you blowing a big ol' cloud out.