For me it depends on what the comments are and from who. If I had a better idea of what the exact words or comments were I might be able to provide some zingers, or witty responses.
Seeing as I don't I will generalize best i can.
If it is a smoker teasing me there is tons of ammunition to shoot back. Most of the information is spread all about these forums and various websites.
If it is a non smoker. Well in my case I have never drank coffee and rarely partake in any caffeine. Most people do, so I can compare my nicotine addiction to their caffeine one.
If it is a kid. Smack the crap outta that brat and teach him a lesson to never make fun of his uncle again. Just kidding.. well kinda. If it's a kid, then it's a kid. Kids make fun of adults, no matter what they are doing. That's the joy of being a kid, no responsibilities to yourself or others because you are going to live forever, and adults are weird.
In most cases I make people laugh and deflect any insults or criticism.
"Hey I have an emergency LED flashlight on me at all times"
"Has anyone ever asked you what you have been smoking? Well I can say I was smoking a watermelon, can you?"
"My PV can me used as a Morse code
device, see S.O.S." <flash led of pv> When they ask if that really was sos or if you know Morse Code, laugh "Of course not"
"PG is used in hospitals and lab tests to kill viruses and other harmfull bacteria, you should be thanking me for saving all your lives."
and my list could probably go on and on... Hope it helps
T