Plants are grown for topiary because they are NOT quick growing.
If you clip a plant, it needs to have short internodes, therefore slower growing.

Bay Laurel (Laurus nobilis) is probably the fastest growing that I know of.

If you have one that grows very quickly it will need clipping very often. As Vincentdunn says, on a fast grower the leaves will be well spaced out along the stems so it would also be difficult to make a neat specimen in a pot. I would recommend box, buxus sempervirens - it grows reasonable quickly once established and clips well, but you won't get a good finished shape established in a single season whatever you choose - even a simple pyramid will take a bit longer than that. The easiest way to do it is to use a wire frame in the shape you want and use a combination of tying in and clipping. Avoid complex shapes if you are a beginner.

I can't imagine bay laurel being any good for topiary though, not in a pot anyway! You will see why when you see a plant!

Privets are the quickest that I know of. Better individually pruned rather than clipped, due to leaf size.

Goldcrest, in largish tub, keep well watered, or why not choose Lonicera nitida baggesons gold, but like steriogram states it will take a while. julien.