Here's the situation. Streetsam's out to shoot your head clean off, using a rifle with an auto-targeting platform installed. In that gun's code to do everything; blow your head off, fire off the secondary weapon, turn on the safety, switch the firing mode, unload the gun, order a soykaf. In any other situation, you might be screwed. Not enough time to hack the gun while you're outside of Full VR. With a Machine Sprite, though? You'll be able to turn on the safety, force eject the magazine, lock the safety controls, maybe even overdraft the bastard's cards by ordering 10,000 machiatos before they even realize the gun won't fire.
Fact of the matter is that you'll be impacting the Physical while in the Matrix just as much as you will be impacting the Matrix while in the Physical. One of the bigger weaknesses of the other Sprites is that they can only really help in the Matrix; they don't know how to use hardware, so they can only really give you access to start taking control of physical machinery. A Machine Sprite's got the knowledge to utilize physical machinery itself, making them extremely useful for helping the rest of your crew. They only have Analyze and Command forms at the start, but they have the most Powers!
So long as the Machine is inside the piece of tech it's targeting, it can help whoever's using it. Once it activates the Diagnostics power, roll double the Machine's rating. Every hit gives the user an extra dice to roll on their test! However, this has limits; if your friendly mercenary only has 2 skillpoints with shotguns, the Machine can only give 2 extra dice, even if it got 5 hits!
With the Gremlins power, the Machine can force a device to malfunction or work improperly. Again, it must be in the device's node, or in a different node that's subscribed to the target. I recommend hacking into potential problem systems before you need to stop yourself from getting killed. Once the Machine begins running Gremlins, roll an Opposed Test; double the Machine's Rating vs. the device's System + Firewall. If the Machine wins, the device will glitch. Fate will decide what happens, maybe a jam, or a faulty reading. If the Machine gets 4 hits more than the device, a critical glitch will occur, either breaking the device, forcing it to reboot, or even sending jolts through the user! If the target's a vehicle or drone, Gremlins can instead immediately force the driver to make a Crash Test. In this case, the Sprite's rating is taken away from the test's dice pool.
When the Machine uses Stability, it prevents malfunctions and accidents from going off, whether caused by a glitch or by a Gremlins/Accident program! Doing this cannot stop critical glitches, but it CAN reduce them to a standard glitch.
This is not a comprehensive list of all the actions a Machine can take, but all the actions that they will be able to use as a baseline. Remember, all Sprites are capable of taking on extra Complex Forms (One for every Three Rating Points), but can not take on any extra skills!