The flashback of when Sgt. Hugo Stiglitz murdered 13 Nazi officers. Major Squick abounds, though some found Fetish Fuel in it, but either way, it's pure awesome.
When Hicox smoothly switches back to English after realizing he's been caught, and then Stiglitz's snarky "Facing the Bullets" One-Liner:
Hicox: Stiglitz?
Stiglitz (in English, to Hellstrom): Say "Auf Weidersehn" to your Nazi balls!
When the theater burns as Shosanna's giant face laughs maniacally on-screen, and Donny and Omar shoot the living daylights out of everyone. Bonus points for Donny shooting Hitler's face into pudding.
The last scene when Lt. Aldo Raine gives Landa a swastika scar on his forehead as Utivitch grins like crazy.
"Nah, I'll prob'ly just get chewed out. Hell, I been chewed out before."
Lt. Aldo Raine: This might just be my masterpiece.
When the Basterds are breaking Stiglitz out of prison, they gun down the Nazi guards, and he just casually sits there without twitching as the guards are being blown away.
The scenes taking place in 1941. They also could double as crowning moment of funny, I guess.
"Champagne? *BANG*"
Winston Churchill's grim, Smoking Is Cool-laden "Brief him."