Ehle 250ml straight tube with diffused downstem and no carb-hole. Why: It is the only one i have.
I chose it because i wanted something simple and easily cleaned. Small so i don't lose the flavour and it is easily tucked away, but no so small that i don't get that "clear" effect after i pull the stem.
For 40€+shipping, i don't think i could choose any better.