In the Star Wars Galaxy, droids are everywhere. Owned by most groups across the various star systems, they are incredibly prominent in the franchise's content and prove themselves to be insanely useful to the characters. While they are often treated like nothing more than a bucket of bolts, droids so often are the difference between life and death for the other characters.
When the characters form relationships with their droids and care for them, such as Anakin, Hera Syndulla, and Poe Dameron, it leads to fantastic bonds, which, in turn, lead to many great scenes where droids become the true hero of the day.
L3-37's Droid Revolution
There is a case that Solo: A Star Wars Story is the most underrated film of the new era of Star Wars, providing a fun adventure, some great character moments, and some fantastic scenes.
One of the most crucial points in the movie sees L3-37 free numerous droids on Kessell, who uprise against the slaver owners and help Beckett's crew to escape with the coaxium. Although Elthree ends up dying in the crossfire, she did ensure the survival of Han, Chewie, and Lando.
R2-D2's Droid Army
When R2-D2 and Ahsoka Tano find themselves captured with Lux Bonteri by Death Watch in The Clone Wars episode "A Friend In Need," R2-D2 was ordered to repair droids harmed in battle.
Rather than simply repair the droids so the Mandalorians could use them as target practice again, R2-D2 changed their programming to fight against Death Watch. He also programmed them to help free Ahsoka, get her lightsabers to her so she could fight the Pre Viszla, and allow for the heroes to escape relatively unharmed.
R2-D2 Repairing The Hyperdrive
As anyone who has watched a Star Wars movie knows, R2-D2 saves the day a lot. He is one of the most important and underappreciated heroes of the Galaxy.
It does not take much for R2-D2 to be a hero, considering how much trouble the non-droid protagonists find themselves in. When the hyperdrive was down on the Falcon as the heroes tried to escape the Empire's grasp on Bespin, R2-D2 was called into action to fix it and, once again, save the day.
IG-11's Sacrifice
Moving onto live-action television, The Mandalorian's inaugural season presented audiences with a slew of brilliant characters, including the Taika Waititi voiced assassin droid, IG-11.
When reprogrammed to protect and care for Grogu, IG became a beloved protagonist, who also sacrificed their life for the greater good. When a stormtrooper unit was waiting at the end of the lava river on Nevarro to take out the heroes, IG went ahead and initiated his self-destruct sequence, killing them all. This then allowed Mando and Grogu to live on another day.
Chopper & AP-5 Finding Chopper Base
Star Wars: Rebels provided fans with by far the angriest droids thus far and one of the funniest in the form of Chopper (whose friendship with AP-5 led the rebels to Chopper Base).
Initially, Phoenix Squadron was set to place their new base on the moon of Berzite. However, after getting stuck on an Imperial ship, Chopper learned not only about the Empire's planned blockade of the system but of the remote planet Atollon. It served as an excellent base for the rebels until it was destroyed in its titular battle in 2BBY.
R2-D2 Fixing Padmé's Shield Generator
Chronologically, R2-D2's first heroic on-screen act came all the way back in The Phantom Menace. Long before he was the friend of Anakin and Luke Skywalker, R2-D2 was just another astromech droid.
When Separatists damaged Queen Amidala's transport ship, and the shield generators went down, a load of astromech droids was sent out to repair it, with only R2-D2 surviving. He fixed the ship, allowing everyone to reach hyperspace, past the Separatist blockade safely. From this moment on, he became a great friend of Padmé, and later, Threepio and Anakin.
K-2SO's Sacrifice
Moving back to the more heavy-handed topic of sacrifice, droids can form distinct and likable personalities. One of the best examples of this is K-2SO, whose sacrifice provided probably the most emotional moment in Rogue One.
With Imperial forces closing in, K-2SO locked Cassian and Jyn in the room where the Death Star plans were being held, and decided to face the wave of troopers alone. In dying, K-2 ensured Jyn and Cassian retrieved the Death Star plans, which essentially played a part in the Rebels' victory against the Empire.
R2-D2 Headed For Help
One of the best aspects of The Clone Wars' is how it fleshed out relationships introduced in the prequel trilogy, not least of all that between R2-D2 and Anakin Skywalker.
When Boba Fett set out for revenge against Mace Windu, he infiltrated a Jedi Cruiser and brought it crashing down, eventually trapping Anakin and Mace Windu in its imploding wreckage. Anakin, placing everlasting trust in the astromech, sent R2-D2 to get help. Not only does the droid save the lives of the two Jedi, but he also does so while fending off the group of bounty hunters attempting to finish off Windu.
BB-8 Saving Finn & Rose
BB-8 is the Disney era's droid and far more prominent in the sequel trilogy than R2-D2 or Threepio, having his fair share of heroic moments in the three movies.
Arguably, the most heroic act was taking the map to Luke to Rey and, later, the Resistance base. With R2-D2 having the majority of the map anyway, the act more suited to the term 'saving the day' comes in The Last Jedi when BB-8 hijacks a First Order AT-ST and saves Finn and Rose from the Supremacy, which was burning down.
Threepio & Artoo In A New Hope
For as long as Star Wars has existed, droids have been saving the day, and way back in 1970, C-3PO and R2-D2 did so much to ensure not the Galaxy was safe.
First off, their entire journey to find Obi-Wan not only got the Jedi Master involved in the Rebellion's efforts, but Luke Skywalker too. R2-D2 also played a part in aiding Luke and his X-wing during the Battle of Yavin. Perhaps the most obvious example of them saving the day was when they prevented the trash compactor from crushing the heroes, which, had they not have done, Star Wars would have had a fairly awful ending.