9. Voice Changing Strip
A companion piece to the franchise-favourite masks, the voice changing strip replicates every nuance of another individual's entire vocal range. It is worn above the throat and allows its user's voice to sound identical to the person of their choosing - provided they have loaded it with a large enough vocal sample.
In Mission: Impossible III, the IMF must pose as Owen Davian (Philip Seymour Hoffman in a surprisingly mainstream role) in order to kidnap him without alerting his security team. To do this, Ethan Hunt not only uses the mask to perfectly replicate Davian's face, but also the voice changing strip to complete the package. To achieve this, Ethan has him read out a poem that is meant to contain all the allophones of all the phonemes of English (all of the relevant speech sounds needed to create most words).
Though this is one of the best gadgets in the team's arsenal, it is rarely used, as, at least from a script writing perspective, it allows both the IMF and their villainous counterparts a little too much power.