If I had to name just one favorite tool, I would pick the bail forming pliers by Wubbers. These are better than any mandrel because the opposing jaws of the pliers can grip the wire while forming.  They are also very useful in creating all sorts - clasps, wire coils and ear wires -  as shown in this past post.

One super example is the Ambroisa Earrings tutorial by the instructor on Beadaholique.  Their video tutorial shows the use of two sizes of round bail forming pliers to create some portions of the beautiful Ambroisa set (earrings above).  The bail forming pliers ensures quick and consistent wire forming. The instructions are here.

Wubbers have now come out with square, oval and triangle ones!  As you can see from the video tutorial, you can make square jump rings and square metal tubes from sheet metal.  The design possibilities are endless.

Here is a nifty square or diamond shaped earring wires tutorial by Jennifer on Youtube.

Before You Go:
Original Post by THE BEADING GEM
Jewelry Making Tips - Jewelry Business Tips