The entire Kaliatek mission. You get your SC-20K assault rifle in the previous mission, but you can't kill anybody with it because they're CIA agents. But the Kalinatek mission has no alarm limit and pits you against a building full of evil mercenaries, so you can go nuts! You don't even have to hide the bodies.
The end of the Abattoir mission. This is one of the very few instances in the first Splinter Cell where you must fight the enemies. The scenario: a group of kidnapped Chinese diplomats and American POWs are imprisoned in a slaughterhouse in Myanmar and scheduled to be executed. Sam having discovered them throws the bad guys' plan off and so instead, Vyacheslav Grinko decides to just kill everyone at once. The American soldiers have been starved for two days and are in no shape to fight. It's just Sam against six Georgian soldiers + Grinko. Depending on how you play, this can turn into a massive shootout worthy of a Hollywood epic movie, or you can fight unfairly by setting up wall mines and using reprogrammed gun turrets to kill the enemies for you.
In the second Chinese embassy mission, causing the explosion of the nuclear bomb's truck (without causing a nuclear chain reaction of course) is quite rewarding.
The train mission. It has some truly original level design, and it ends with a dynamic escape by Sam, catching a rope just in time while the enemy helicopter shooting at him is destroyed by a missile fired by the Osprey.
While the action in it is fairly standard infiltration, the Jerusalem mission displays an amazing ambience, helped by the music.
The end of the second last mission. You need to bring in the Big Bad alive, and he's in an auditorium pre-recording a speech in case he's killed by an assassin just like you, and he's surrounded by his loyal soldiers. How do you get him out of there? By walking behind him on the stage, coming out from behind the curtains and grabbing him, and then calmly walking out because his soldiers are too afraid to shoot with him in the way. It is a moment of incredibly rewarding stealth.
The entire Panama bank mission. A very open-ended mission that allows you multiple paths of entry into the bank, a wise-cracking Boxed Crook talking you through breaking open the vault, and Sam pulling off a robbery that would impress the Ocean's Eleven crew. And the best part is that stealing the money isn't even the point, it's just there to throw off the investigators.
Fisher: So Lambert, now that I'm holding 50 million bucks, I think it's time we talk about that raise...
Lambert: Hmm. 25 cents an hour and not a penny more.
The Mexican Standoff at the end of the Tokyo Bathhouse mission. "Blood is thicker than water, Sam. I know you. And I know you wouldn't shoot an old friend." Sam has two potential responses to this statement by Douglas Shetland. The first is to shoot him. The second is to put his Five-Seven away. Shetland goes for his own gun, and Sam stabs him through the heart with his combat knife. Either way ends with Sam chucking Shetland's corpse through a paper wall to fall and splash unceremoniously into a bathhouse vat, with the Bond One-Liner "You were right, Doug. I wouldn't shoot an old friend." The implication of both eventualities is awesome.
The flashback scene. Sam eases little Sarah's fear of monsters in the dark with child friendly euphemisms that boil down to "Once you get used to the darkness, you can murder people easily because you can see them and they can't see you." Then, a group of armed criminals break into the house, forcing Sam to kill one with hand to hand then kill the other two with a Mark and Execute.
Sam taking on Third Echelon Splinter Cells in Conviction during the attack on the White House. They all know how good he is. He's a legend. And he cuts through these guys like a hot knife through butter.
Even before in "WELCOME HOME" which has Sam assaulting Third Echelon HQ.
Receptionist: I'm sorry sir, but I'm afraid the office is closed for the evening.
Fisher: I'm here to see Tom Reed.
Receptionist: Mr. Reed is currently unavailable. But if you'd like to make an appointment Mr...
*Fisher blows the C4 to knock out the building's power and begins his assault on Third Echelon*
*The best the receptionist can do at this point is to hide under her desk, so she does.*
During the mission you fight soldiers using similar gear Sam used, including his high tech goggles, but even with all their gear and overwhelming numbers they are still scared of Sam. He's just that good.
When Fisher has to "secure" vice-president Samson.
Vic Coste saving Sam's life in Iraq. Unexpected Gameplay Change or not, this guy is not a spy of any sort, but goes against orders to save his commanding officer's life because they're good friends.
No mention of the "Sam's Rage" segment? For those unaware, it's the part at the end of the Third Echelon HQ mission where Sam listens to a recording of Lambert admitting that he faked Sarah's death. Between the music,the visuals,and the voice acting you really feel the grief and anger Sam is going through upon learning that his late best friend betrayed him. This culminates in Sam walking out of the building as the game gives you unlimited Mark & Executes allowing you to gun down every enemy in sight with the press of a button, all while the building is exploding around you. Even people who don't like Conviction admit this is the one of the greatest scenes in the whole series. Wanna make it even more badass? Walk as slow as possible and only use a shotgun.
At the start of Blacklist, Sam and Vic's helicopter is blown out of the sky. Instead of panicking, they adapt to the situation, grab some weapons and try find and disable the signal jammer which has rendered the Guam base defenceless. Later, Vic's fast enough to tackle Sam to the ground and save him from a grenade blast which puts him in a coma.
In Blacklist Sam successfully breaks into the former US Embassy in Tehran, the Real Life base of Iran's feared Special Forces and lives. His escape just adds to the audacity of the infiltration with Grim providing cover with the UAV, blowing away hostiles as Briggs and Sam speed through Tehran with Iranian operatives on their tail.
Also when Sam breaks into none other then Guantanamo Bay and when he defies Caldwell's orders not to land in Denver and breaks into the Site F bunker, one of the most secure installations in the United States
The Louisiana mission where Sam traverses through a gas refinery which is burning down around him, re-activates the safety systems which prevent the massive fire from spreading to other refineries in the area and then is able to hunt down the Engineer leader overseeing the attack with Charlie causing the latter's getaway vehicle to crash by reactivating the entrance barrier.
Kobin of all people gets one. When the engineers try to crash the Paladin with a computer virus, and one of the pilots is knocked out, Kobin keeps the plane up in the air while telling Sam how to purge the virus and restart the plane. Later, he's able to put these skills to use evading the air defences around Colorado to infiltrate Sam and Briggs into Site F
Sam escaping Sadiq's trap in Iraq when infiltrating their training camp. He runs through a burning building as a UAV bombards the place, rappelling up to the escape chopper barely in time as the building he's escaped from collapses.
The Briggs missions. Preventing SVR's Voron division from stealing part of India's nuclear arsenal as the Blacklist attacks are going on.
The gunfight with Voron operatives while recovering Kestrel from the abandoned city in Russia.
Briggs being unmasked in the Colorado, subverting the initial belief that Sam got caught. At that point you know Fourth Echelon has finally caught up with Sadiq, one of the first true Magnificent Bastards in the franchise.
Aide: I'm sorry, the President is occupied with an urgent matter and won't be able to speak with you. Grim: Tell her it's Fourth Echelon. Aide: She knows. Sorry, Grim. Grim: Look, I know you think you're special because you sip lattes with the POTUS, but I have a lot of friends on Capitol Hill... Aide: Are you threatening me? Grim: No. Get me the President if you ever want to work in D.C. again.Now I'm threatening you. Aide quietly scuttles away
EXERCISE FIFTH FREEDOM
Briggs killing the Secretary of Defense in order to ruin Sadiq's final plan. Up until this point, Sadiq's been a completely unstoppable and unflappable Magnificent Bastard but he clearly begins to crack when Briggs denies him access to the classified information he's been after.
Sam's takedown of Sadiq, one of the first true Magnificent Bastards of the Splinter Cell series. First, disguised as a base employee, he kills Sadiq's Mooks, then after sneaking up on him, fights him, cripples Sadiq by getting control of his knife and slashing an artery and at the end, he subverts his Roaring Rampage of Revenge and drops Vic's karambit in the snow, denying Sadiq a My Death Is Just the Beginning and causing a Villainous Breakdown. Seeing Sadiq afterwards, completely subdued and broken in prison makes it all the more sweeter.