Wow. Where do I start?
I have been very lucky over the years to be present for some serious PC awesomeness.
There were so many moments...by so many characters...how do I determine which was the most impressive?
What makes it even harder to choose is that what makes a character's action impressive to me has a lot to do with how the player, and GM role-played the sequence. A lucky critical hit roll means nothing to me. A successful skill roll is only interesting if the player used the skill in a creative, and unusual way.
To impress me - to really impress me - a player, as their PC, needs to go somewhere deeper with the character, and the story.
My ex-wife's long running D&D-But-Not character, the Elven Fighter/Magic-User CerenDee Wind-Drake, had a reputation for being able to subdue opponents with naught but a heart felt conversation. Her ability to parlay was a stunning as her magic. Her words sharper than her sword.
After a number of successful diplomatic exchanges with different people, and humanoid monsters, she was fairly certain almost any encounter with an intelligent being could be handled peaceably.
Upon encountering an Illithid, or Mind Flayer, for the very first time (with no prior knowledge of what one was) she attempted to reason with it, and perhaps reach an understanding between the psychic nightmare, and her party. A fellow party member warned her these creatures were simply evil with a capital 'E', and that they were not to be trusted. She tried anyway.
The Mind Flayer, who had a captured Human villager in its clutches, agreed to disengage from the current battle, and leave the area, but only after it had fed. It claimed to be injured, and starving. She agreed, and the Illithid sucked out the mind of the villager in a flash. The innocent man dead, it held to its word, and departed.
CerenDee was crushed, and many people in the party chided her for not listening to them about the Mind Flayer. Torn by her guilt over allowing the villager to perish in a horrible way, and firmly believing that not every encounter needed to end in bloodshed, Wind-Drake considered quitting the Order of the Winghorn Guard. She believe she had failed miserably in her attempt to uphold the Order's principles.
Her team leader had a private talk with her in which he said (paraphrasing), "I have not in all my years in the Guard seen anyone who is as steadfast, and true to the Order's ideals as you. Don't let one incident, no matter how tragic, stay you from your beliefs. Never forget though, that not everyone in this world shares those beliefs. So people, some things, are truly, deeply evil, and can not be redeemed. If you believe in fighting for justice, protecting the defenseless, and letting peace prevail, you must be willing to fight for your beliefs as much as you are willing to talk about them."
The moment had a profound effect on the character, and the campaign, tinging our light-hearted action-adventure game, into something more serious. The stakes were higher, and they would keep going up. Dealing with different enemies in different ways, standing up for what you believe is right even if others don't agree, and handling the consequences if you're wrong become key elements from that point on.
In order to prevent the Imperial Empire from warping his scientific, and technological genius into a terrible weapon of mass destruction, my friend Phil's character - Professor Gustov Frahkeen - along with the rest of the characters in our Star Wars: Ever The Brave campaign, decided to sneak aboard the Imperial Research Outpost housing the collected data, and the prototype of Frahkeen's invention and neutralize it.
The plan called for a multi-part, multi-PC affair with an Alien Scientist, and an Astromech Droid hacking the Outpost's computers to kill the security sensors, and erase the data on the device. The Young Jedi, and Brash Pilot were charged with escorting Prof. Frahkeen to a room adjacent to the one containing his device so he could send a remote signal that would disable it, and fry it's circuits. The Smuggler, and his Droid Engineer companion, in two different ships, would be the 'wheel men' for a quick get away, or to cover each others escape should a squad of TIE fighters show.
All went by without too much of a hitch until Prof. Frahkeen, seeing that they had implanted his invention into the warhead of a large missile, had a psychotic alternate idea. The player, my pal Phil, simply said, "I said the signal, but not the one we intended."
All eyes turned to Phil. A hush fell over the group. The silence was deafening.
"Phil...", I began slowly, "What did you do Phil?"
Phil smiled, and took a deep breath as the rest of the group exchanged panicked glances. Had the mad scientist truly gone made?
Straight faced, I spoke with exaggerated calm, "Phil, can I see you in the kitchen?"
After getting clear of the rest of the group I said, "Now Phil..", at which point he began to tell me, in earnest, how if he merely shorted out the invention's circuitry, the Empire could still reverse-engineer the device to see how it worked. The plan was a delay, not a solution. I said Okay, and wondered where it was going, although I had the sinking feeling I knew.
Phil said that he sent a 'Detonate' signal to the missile's onboard computer. Basically, he told the bomb to go off. The resulting explosion would destroy the device, and possibly the entire station with it. You see Gustov's invention was a Star Wars version of the Genesis Effect from Star Trek II: The Wrath of Khan.
It doesn't stop there.
We return to the rest of the group, Frahkeen sends his signal, and then immediately contacts all his team members and tells them it would be best to depart the Outpost. They ask him to confirm that the signal was sent, he says yes, but it is imperative that they leave at once.
Unfortunately, our Alien Scientist, and the Astromech hadn't returned to the ship yet. They'd been spotted, and the Scientist used his species' bizarre appearance to appear to be a non-sentient lab animal. Our Brash Pilot doubled back for him, as our Young Jedi made sure Frahkeen got back to the team's Light Freighter. The Smuggler confronted Frahkeen about what he'd done, and Frahkeen came clean, reminding everyone that they probably only had seconds to go at this point.
By unanimous decision, the Freighter, containing the Smuggler, the Young Jedi, and Frahkeen, departed immediately. The Brash Pilot grabbed the Alien Scientist, and the Astromech droid, and the group fought their way to the Droid Engineer's smaller scout ship. The Astromech was badly damaged, and the team member took some bumps, and bruises as well. The Droid Engineer, the Alien Scientist, and the Astromech's remains took off in the scout ship while the Brash Pilot jumped into her X-Wing fighter.
They all sped away from the Outpost as quickly as possible, but it wasn't quite quick enough. The invention exploded, which blew up the Outpost, resulting in the discharge of a powerful energy wave, that in turned blew up the gas giant the Outpost was orbiting. The resulting gravitational disturbances, and shock ways messed with the PC ships attempting to jump into Hyperspace.
The Freighter was lightly damaged by managed to limp to a rendezvous point just beyond the end of the star system. The Scout ship was more heavily damaged, but salvageable. The X-Wing actually made the jump to Hyperspace, but ended up flung over 25 parsecs from her intended destination with a fried Hyperdrive.
It was a desperate action, by a put upon man. Phil did an excellent job of adding Humanity to the otherwise cliche' trope of the Mad Scientist. He had to do something to prevent his genius from being abused by the Empire, and he had to do some with permanency. Though he didn't think the action through perfectly, he did what he needed to do.
They still talk about this campaign, and this particular instance, to this very day.