Guess i'll start. This was my favorite pipe back in the day
We called them submarine pipes cause of their streamlined resemblance to a submarine.
Very simple to make. Just cut one co2 cartridge (empty) off to form a bowl. Then insert a metal screen from a water faucet into the bowl. Next drill a hole in the other empty cartridge just the right size for the neck of the of the bowl.
-Simple and cheap
-Tastes of metal
-Impossible or hard to clean