Intuos 5 or a cintiq.
Also lenovo is coming out with a 13 inch wacom enabled touch screen in the next couple of months, it will retail for about $350. To give some perspective, a 12 inch wacom cintiq is $999, so the lenovo version is quite a good price.
I personally use a cintiq, and own 2 intuos 3, an intuos 4 and have worked on an intuos 5 and a bamboo.
All are very capable. You have to ask yourself if you like drawing on the screen or leaving the screen free and using a tablet. Some artist use both.
Starting off, it might be best to get a good bamboo and after you find you like the workflow or build up the skills, upgrade to a more expensive intuos 5 or cintiq (or toss in the lenovo when it comes out).
The mono price tablets, which are very cheap are also pretty darned capable for their price point, though Wacom always has the best pen input and should be your first priority in picking a tablet brand.