My Bunny Bites and Lunges!
Because rabbits bite or nip and lunge for several different reasons and because they are as individual as people are, there is no single way to stop a rabbit from inappropriately expressing her opinion. The most important thing to remember is that rabbits do not generally vocalize like dogs and cats do; they have to use their teeth and their paws instead. Where a dog might growl at you to say "stay away," a rabbit will try to run away, if possible, and will usually back up and then lunge and bite if not. So, before you choose a response to the rabbit's action you need to determine what the rabbit is trying to say. The two main clues are the strength of the bite/lunge and the rabbit's actions just prior to delivering the bite.
A gentle nip is usually the rabbit's way of telling you that you should either move or that you should go back to doing what you just stopped, usually petting. How you respond to this is going to be determined by whether or not you find this kind of communication acceptable. The easiest way to tell a rabbit that they have used their teeth too firmly on your skin is to "eek" at her. When a rabbit wants another rabbit to move, she will generally nip which, to another rabbit, only results in a gentle tug on the fur. If the nip is too hard, the offended rabbit will emit a short, fairly loud, high-pitched "eek." If you do the same, your rabbit should understand you. There are, of course, stubborn rabbits who will understand but choose to ignore you, especially if they have been getting away with nipping for some time. Since the rabbit wants your attention in some way (move, pet me, etc.) you can simply move the rabbit away from you to show your displeasure. This is especially effective if you are able to turn most of the way away from the offending rabbit. This is rabbit body language for "you offended me, but if you behave nicely we can still make up." The key to this is to only turn mostly away, not 180-degrees since that signifies that the other rabbit has offended beyond a simple fix.
Harder nips are more often intended to be punishment of some kind. Dominant rabbits will generally issue a quick, hard bite to a rabbit who has somehow broken one of the dominant rabbit's rules. These bites don't generally break the skin but they can leave some spectacular bruises! "Eek"-ing might work to curb the behavior, but since you are dealing with a dominant or bossy bunny, it is much less likely to work since she probably doesn't care as much what your opinion is. To stop these bites you will need to figure out what your rabbit wants and then not give it to her. For example, if the rabbit bites to be put down, you need to keep holding her until she has behaved for at least a few seconds. If, like many people, you release the rabbit out of surprise, try to keep one hand on her and then pick her up again immediately. If you allow her to go free, she will learn that biting equals reward (freedom).
Hard nips can also be delivered out of fear. This is usually fairly easy to recognize since the rabbit usually tries to get away first and will only bite when she feels trapped. In these cases you want to be careful not to punish but to reassure. Try getting down on the rabbit's level and talking softly. Again, you can always "eek" at the rabbit. It may be enough of a surprise to break the fear, especially if the fear was caused by a sudden noise or movement and not and ongoing thing that is still frightening the rabbit. We have recently spent a lot of time working with a foster rabbit, Pippin, who was probably abused before coming to us and was very afraid of humans. He literally bit at you if you sat two feet away and twiddled your thumbs. "Eek" worked very effectively with him and I could literally see him stop and think. It didn't stop the behavior, but over a few weeks it greatly reduced his biting reaction. Unless you foster or take in a rabbit from somewhere other than a shelter or rescue group you will likely never see a rabbit who is as fearful as Pippin, though, so you can expect your work with your own rabbit to move much more quickly.
In the event that you have run into a particularly stubborn rabbit who simply will not give in, you can try using a spray bottle. When the rabbit bites, spray her in the face with water. Since rabbit fur is so dense and is designed to help keep rain away from their skin you will need to set the bottle to "stream." Alternatively, most squirt guns work to penetrate the rabbit's coat. The goal here is something like tossing water in the face of an hysterical human - shock.
Unless you are dealing with a fearful rabbit, the main goal should be to teach your rabbit that she will not get what she wants by biting. This takes consistency on the part of everyone dealing with the rabbit or you may find that your rabbit won't bite you but will bite your family members or guests since they don't object in terms that the bunny understands.
In summary, your job is to figure out the rabbit's goal or reason for biting and then figure out how to deny that goal. Most rabbits learn fairly quickly that bonking you or slapping you with a paw will get you to move without getting the rabbit in trouble or that you can be "taught" to do things the rabbit's way by some method other than biting.