Every house should have a portable fire extinguisher. Even a small one for one-time use is better than nothing, but for most purposes the recommended size is a 2-A, 10-B:C, which indicates both the size of the extinguisher and the type of fires it is effective against.
Larger is generally better but it needs to be usable by all the adult occupants, so you might consider a large extinguisher's weight. Extinguishers should always be mounted not more than 5' off the floor in an accessible, visible location. Don't put it away in a cupboard to be forgotten.