What do you think are some bad manners?

Swearing
Sticking your fingers in your own or anyone elses oraphises in public
Acting without respect
Talking really loudly at stupid hours
Acting with discontent

And above all...

SPITTING IN PEOPLE'S FOOD!

All these stuff in front of other people basically in public:

-Swearing

-Burping

-Farting

-Picking your nose eww!

-Not knocking before entering someone's room

-Not saying hello - it's just common courtesy!

-Not saying Please and Thank you

Spitting in general. It is truly disgusting.
Mobile phones not turned off in the appropriate areas - hospitals, libraries, churches, cemetaries etc.

But above all, able bodied people using disabled parking spaces. There is NO DEFENCE.

Eating out of somebody elses nose.
It's anti-social too.

Not saying thank-you when someone does something thoughtful for you (even if you didn't ask for and don't like it!).
Licking the plate at the table is pretty bad (I had a boyfriend once who came to my family's house for dinner - we ate something that had vinegar added - he licked the vinegar off the plate at the end - YUCK! not very impressed!).

talking with food in your mouth. omg! i can't stand it... its disgusting.

picking your nose at the table or any time you're not alone, making out with your S/O in front of your family, talking about what a big shit you took earlier while you're at the table, or how clogged the toilet is, clipping your toenails at the table, making certain jokes around people who those jokes pertain to, going "ugh!" in a preppy manner if someone bumps into you by accident, not apologizing if you bump into someone, you get the point

Talking on your cell phone while having breakfast/lunch/dinner with people. Unless it's family or related to your job.
Not saying please and thank you. That's one of my biggest pet peeves. My best friend does this sometimes and it annoys the s*** out of me.
Strangers making rude comments about someone's looks to their face. I don't understand why anyone would do this and not expect a bad reaction.

The grossest of them all:chewing with y our mouth open and digging your nose in public.