Answer: Ratchet
There are five Autobots: Optimus Prime, Bumblebee, Ratchet, Ironhide, and Jazz.
Rachet is the medical Autobot. Brawn, Air Raid, and Crossblades are all Autobots but are not shown in the movie. In the film, Ratchet takes form of a search and rescue Hummer H2. His weapons include a rotary saw that emerges from his left arm, and can transform his right arm into a machine gun. Ratchet also has an assortment of other tools at his disposal; he uses a red laser to scan and try to calibrate Bumblebee's voice box as they are introduced to Sam Witwicky and Mikaela Banes. He also has enhanced senses.