Like some one else said, letting her think that it's her idea can make a big difference (works with husbands too, LOL). My daughter was very attached to her binky and couldn't sleep with out it (we limited it to nap/bedtime). Her 3rd birthday came & went and I was beginning to despair of her ever giving it up. We started talking about her being a big girl and not a baby and how big girls don't use them, etc. She would say things like, "When I'm bigger and don't use my binky anymore . . ." but it was always in the future for her. We don't do Santa so I couldn't use that, but when she didn't get one of the things she really wanted for Christmas that year, I told her that if she slept all night without her binky she could have that toy. There were several more weeks of talking about it. She didn't whine or demand, she would just comment, "when I don't use my binky anymore, I can have my car, right?" I always assured her that yes, that was true. Finally one day in February she announced that she was ready to sleep without her binky. She went to bed very excited. It took her longer than normal to fall asleep, but she did, and the next day I took her to Toys'r'Us and picked up her toy. She never asked for the binky again!
Now I don't know if a 2 year old can think abstractly enough for this approach to work, but it sure did for us.