Can't get that dank smell out of your bong? It reeks, doesn't it? You've rinsed a milion times over, and it's still putrid.
Enter: baking soda. Costs less than a dollar for a whole box, and out of the many uses it has in the home, getting rid of funky smells is one of them!
After you've already cleaned out your bong with hot water/soap/rubbing alcohol/salt/whatever, add about a teaspoon of baking soda to your bong. More is not better; this stuff works well in small amounts. Add some water (cold or hot, doesn't matter). Shake, shake, shake yer booty...errr, your bong (DON'T BREAK IT!!!), and empty it out. You can do it once or twice, but I find doing so twice generally does an awesome job. Rinse it out REALLY WELL with cold water as baking soda will leave a white crust film if it's not properly rinsed.
And your done. The smell is completley gone.
