A Gentleman's Duel

A 2006 CGI short film from Blur Studios, A Gentleman's Duel is about two gentleman (the Englishman Weatherby and the French Dubois), rivals for the love of a beautiful and wealthy woman, find that the only way to settle their grievances is with a duel. With giant steam-powered robots.

Tropes used in A Gentleman's Duel include:

Abnormal Ammo: Fifi
All There in the Script: We never actually hear the names "Dubois" and "Weatherby"-- they only insult each other (Weatherby calls Dubois "the Marquis du Manstrumpet" and Dubois calls Weatherby "Sir Dingleberry").
Badass Mustache: Both men have pretty good mustaches, though Dubois' is especially fancy (and he loses his temper when it's disarrayed by a Glove Slap).
Bring My Brown Pants: Used as an insult by Dubois.

"Fifi says she can smell the fear (Fifi yaps)-- in your pants!"

But Liquor Is Quicker: Used as an (weak) insult by Weatherby when Dubois offers the lady champagne:

"Oh, of course, alcohol-- the French recipe for romance!"

Did Not Get the Girl: Both men sheepishly run off when they think they've killed the lady.
Distant Reaction Shot: When the two mechs slam into each other and explode.
French Jerk: Dubois, in spades.
Freudian Slip: Weatherby, Distracted by the Sexy:

"Your grace is only matched by your boobies-- I mean your beauty!"

Gainaxing: Used to parody the Bad Vibrations moment in Jurassic Park.
Glove Slap
Good Old Fisticuffs: Before the judo, wrestling, and missile attacks are broken out.
Groin Attack: Both on the mechs and on Weatherby himself (when his mech breaks he ends up with an electric eel in a very bad place).
Humongous Mecha: Duh.
Impossibly Low Neckline: The lady's dresses.
The Jeeves: The lady's butler is very good at protecting her from collateral damage.
Kick the Dog: The butler throws a shoe at Fifi for interrupting his vigorous bout of Rescue Sex with the lady. Not like she didn't deserve it.
Knockback Slide
Marshmallow Hell: For the butler, when the lady panics.
Mid-Battle Tea Break
Mister Muffykins: Dubois' poodle Fifi.
Nice Job Breaking It, Heroes: Over the course of the short film the gentlemen manage to sock the lady in the face repeatedly, destroy much of her estate and part of her mansion , and apparently kill her.
Pre-Ass-Kicking One-Liner: Both men get pretty ridiculous ones.
Psycho Electric Eel: Weatherby's mech uses some kind of electrogenic fish to power a Shock and Awe attack.
Rocket Punch: Dubois' mech.
Steampunk: Again, duh.
This Means War: Uttered by Dubois.
Tom Kenny: Voices Weatherby.
Troperrific: Look at this list, and consider that the film runs roughly seven minutes.
Urine Trouble: Fifi adds insult to injury after being fired at Weatherby.
Viewer Gender Confusion: Fifi piddles (and humps shoes) like a male dog. Undoubtedly due to Rule of Funny.
Volleying Insults: "Knicker nibbler!" "Poodle piddler!" "Monkey spanker!" "Cheese pirate!"
X-Ray Sparks: When Dubois is hit by Weatherby's eel-powered attack.
You Can Barely Stand: After their mechs blow, both men crawl towards each other to fight to the end -- until they realize they might just have killed the woman they fought over, and then find the strength to run off.
Your Mother:

Dubois: What would you know of love?
Weatherby: Your mother can answer that, Monsieur le Poopypants!