Oster and Andis both make good clippers, but you do have to spend a fair amount of money for them (usually about $200 and up). Rabbit fun can be hard to shave and can do a lot of damage to to blades. Get a clipper where the blades are easily removed so you can change them regularly without much fuss. Buy a few blades in case one gets dull or too hot when you are working. You do need a powerful clipper so you can do meaningful work. As you will be dealing with matted (and dirty) rabbits, it is important to take good care of the clippers to keep them working well. It is generally recommend to only clip a clean animal, but with matted animals, you don'e have much choice.
If you don't know a good place to get a good set, talk to some local dog groomers and ask where they get their equipment. Good groomers will know the good places to go. Talk with the owner/employees of the shop. They should be able to asnwer your questions and show you how to care for the equipment. They may even be able to sharpen the blades when you need it done.
A good pair os sheers (scissors) will be good to cut away some of the mats that are not as close to the skin and to cut the fur that has been shaved apart to make it easier to get off (one giant mat is a pain to get off).
You may want to talk with a rabbit savvy vet about what kind of shampoo is safe for bunnies. Some rabbits are really dirty under the matts and may need a bath to help them out. This should only be done when absolutley necessary. Sometimes, wetting the matted area a bit can help to work the knots out and get some of the dirt out.
