I'm just wondering, if you take drugs occasionally, is there still a risk of addiction?

Yes: Different drugs seem to have different addiction potentials, some drugs it takes one high or one use, other drugs seem to have less addiction potential, but it also varies person to person.

Yes: There is always a risk for addiction even with occasional use. Here's a breakdown, provided by Herb Kleber, MD: 33% chance with nicotine, 25-30% chance with heroin and other opioids, 20% chance with cocaine, 10-15% chance with alcohol, 9% with weed.