Long term damage from smoke inhalation, cancer, Heart disease and death.
I reckon the main danger is death.
Apart from that i suppose nicoteen stains on your index finger.
It gives you terrible lungs, you are more exposed to lung cancer, if you are pregnant you might kill your child, you will affect other non-smoker's health system, you will always smell of cigarettes.
Largest danger might be lung cancer. That's probably what you hear most of. besides that, you're risk of getting a heart attack might increase (less CO2 transported in your veins) as well as the risk of having a stroke.
You will get Cancer and you will Die. the cigarette smoke mutates the delicate cells in the lining of your lungs, and they become deformed and cancerous. you will get a build up of tar in your lungs. The poisons which are in the cigarettes will also affect your skin and your hair and your teeth and everything else in your body. you should drink lots of water and orange juice and try to cut down or stop. I don't know why but I reckon that fatty food is also quite excellent. The human immune system is pretty excellent and can get rid of most crapola from our bodies, but not if you smoke heavily over a long period of time. Once it is out of your system you will not crave it so much and you will be an 100% better person to be around. Even though you have done damage to your body it will be better not to do anymore. Excellent Luck!