One very popular stencil film is Oramask 813 is also known as a masking material. You will see lots of recomendations for either Oramask 813 or Oramask 810 within social forums on Facebook for crafters. If you are using an airbrush technique, you will love the 813, as it rarely comes unstock, and when weeding, there is little issue with seeing the cut lines to weed it out. Oramask 813 has enough adhesive that it rarely comes unstuck, and the stiffness of this film gives it enough strength so as to not damage the stencil. Oramask 813 performs perfectly with intricate cuts and handles very well. Oramask 813 is great when used on glass and using a small sandblaster, and holds up nicely, conforming to rounded surfaces very well. Removal is pretty easy, a hair dryer - not a heat gun and it pretty much lifts off.
Remember with the stencil film you will also need a transfer tape.
You can find Oramask 813 here. Oracal Oramask 813 Stencil Film
and you can find Oramask 810 here. Oracal Oramask 810 Stencil Film
a great transfer tape that works well with Oramask 813 can be found here ATC 65 Clear Application / Transfer Tape (high tac)