Big Bad Ensemble: The Ogre Phantom and Buijin Gaim, who are unconnected to each other.
Big Damn Heroes / Villainous Rescue: Right when Bujin Gaim is about to finish off Gaim and Baron, Zangetsu appears from out of nowhere and drives him back before ordering the two Beat Riders to go and help Wizard while Zangetsu himself takes on Bujin Gaim. Knowing how powerful/scary Zangetsu actually is, Gaim readily accepts the help.
Borrowed Catchphrase: Using the Legend Rider Lockseeds apparently makes you borrow that Rider's Catch Phrase; Micchy delivers Shotaro and Philip's "Now, count up your crimes!", Kaito uses Eiji's trademark Kiai "Seiya!", and Kouta and Haruto say "It's showtime!" in unison. The only exception is Takatora, who starts to deliver Gentaro's "It's space time!" but stops partway through and says "...And that's as far as I'll humor that notion."
Chekhov's Boomerang: During the movie, Shunpei reveals he made a ring for Wizard. He gives the ring to Haruto, but it turns out to be a dud...until the Hope Ring activates.
Composite Character: The leaders of the Warrior Gods' factions are based off of real figures from the Sengoku Jidai, but are portrayed as alternate universe versions of Rider supporting characters. For example, OOO's faction is lead by Oda Nobunaga, who's portrayed by Hiroaki Iwanaga (AKA Akira Date, the first Kamen Rider Birth).
Continuity Nod: As mentioned above, OOO's faction is led by Oda Nobunaga. A central character in OOO's segment of Movie Wars Core was a clone of Nobunaga.
Eleventh Hour Superpower: When Bujin Gaim traps them inside the sacred tree during the climactic battle, the other Bujin Riders imbue Wizard and Gaim with all of their power, allowing them to break out of the tree and deal the finishing blow to Bujin Gaim.
Enemy Mine: Zangetsu goes to fight alongside the Beat Riders against Bujin Gaim as he becomes aware that the latter is killing off all of the other Bujin Riders and has targeted the Beat Riders next, and their deaths would result in the loss of Sengoku Drivers (and considering Zangetsu's characterization later in the series, he may also have not approved of Bujin Gaim's actions).
The Good King: Ieyasu wants to be this to a nation united. He's more than willing to pick up a sword in battle, even against Bujin Gaim, and openly states that he fights to protect and feed his people.
Mega Manning: By combining the Bujin Riders' collectibles with raw Lockfruits, Gaim, Baron, Ryugen, and Zangetsu gain access to Legendary Rider Arms for the climactic battle.
The Ogre Phantom can use the abilities of the Phantoms he's consumed.
Mistaken Identity: After Gaim assumes Wizard Arms, Nitoh confuses Kota for Haruto when the latter two both use Wizard's pre-battle catchphrase.
Kota and Bujin Gaim get mistaken for each other several times. Justified as they're alternate versions of one another.
Buijin Gaim may or may not have mistaken Mai for the Priestess of Fate. We'll see.
Mood Whiplash: At a dramatic moment, Wizard decides to use the ring Shunpei made for him. Things suddenly turn comedic when the ring fails to work.
Morton's Fork: The false Koyomi is this to Haruto. If Haruto destroys the false Koyomi, it will destroy the Hope Ring, causing him to despair. If he doesn't, he'll fall into despair anyway because she's destroying the city. Haruto ultimately Takes a Third Option.
Nice Job Breaking It, Hero: Zangetsu interferes in what he thinks is a fight between Gaim and a strange Rider he's never seen before. Only after he pulls a Villainous Rescue does he realize that the Gaim he saved was not the Gaim from his world. Zangetsu has barely enough time for this to sink in before Bujin Gaim promptly turns on him. The sad thing is, Bujin Double had the upper hand and stood a very high chance of actually defeating Bujin Gaim right before Zangetsu stepped in and gave Bujin Gaim the vital opening he needed to kill Bujin Double.
Not so Fast, Bucko!: The end of Wizard's story. The Ogre Phantom is defeated...but then Beast is abducted by Buijin Gaim.
Outside-Context Villain: While the origin of the Bujin Riders isn't revealed, Bujin Gaim was this in the context of his world, as he was the only Bujin who didn't have a general behind him and acted on his own, and had an army of kaijin instead of humans, which puts the other armies at a severe disadvantage.
Schizo Tech: The Sengoku world is based off the Sengoku Jidai period, but it has things like guns, cars, and electric guitars.
Self-Duplication: This is normally one of Wizard's powers, but there is an important example in this movie: When the Ogre Phantom enters Haruto's Underoworld, Koyomi's and Shunpei's rings activate to summon...Haruto in his Wizard suit. This allows Wizard to Engage with himself and dive into his own Underworld.