In a recent video, a Chik-fil-A employee courageously jumps in to save a woman from a carjacking attempt.
In the video you can see the employee drag the carjacker POS from the car and then subdue him with a choke until the carjacker surrenders.
Regardless if you carry any type of weapon on your person for self-defense, you should always have a toolbox of empty-hand skills.
Some of the most basic and practical skills to have are Choke/Submission techniques from Brazilian Ju-Jitsu.
Rear Naked Choke
Arm Triangle Choke (Anaconda, D’Arce Choke)
There are also a SHIT TON of Clothing Choke holds that can be very useful, in particular the T-Shirt and Hoodie Choke.