Things I hear frequently referred to on the net or in the show...and then on the net.
Can't think of any for Kuuga and Agito (except maybe Gills' screaming and that the guy who wrote it hasn't really done anything else as good.)
-"Don't molest the lawyer"
-"Time Vent fixes everything"
-"I'm vexed" (Thank you TV-N)
-Season of belt-jacking/belt stealing/"I wonder who steals the belt today" etc.
-"Yuria Haga is the sex" or "Yuria Haga is so ugly" or some variation of the words.
-Usually some derivation of "Leangle is a total douche"
-"The second half sucks/pales/is s***/I like to make up my own ending compared to the first half"
-Zanki's naked man-butt
-Anytime the belt speaks English. Particularly RIDER KICK as you can see in this video
^^Skip to 0:45
-Emo/Yaoi/Hell Hoppers' existence. Also, Tokuyama himself is now a walking "I'm clearly a toku actor"
-Not really sure why but a lot of people call Drake gay for some reason.
-"Grandmother said this...."
-Pick a catchphrase. Any catchphrase (Obviously "Ore Sanjou" is the most popular)
-I've heard "Deneb Candy" tied into so many random sentences at this point.
-Tatsulot/Bae obvious connection
-753. Nago is a walking meme. Honestly, you could say anything about him.
-"Where's Bashaa Fever/Wake Up Three?"
(Oh boy here we go)
-Let's get it out of the way now. Narutaki...just..just Narutaki
-"This is all Decade's fault"
-"Decade...you have destroyed this world as well."
-The Decadriver itself is a good one as well as the cards. Lots of us sure like using the "(blank)" RIDE....(insert name. Repeat letter for Final Attacks)
-Mega Man Decade. Pokemon Trainer Diend (or decade is Sora or that Diend is a refrigerator, etc.)
-"I'm just a passing-through Kamen Rider. Remember that."
-"Decade had no story"
(I'm hearing that more and more since Iga's review came out)
-Complete Form looking ugly as sin to most fans.
-This series being Gackt's love series (like how TMR was to Gundam SEED)
-The Natsumi thumb thing
-"Will Kuuga henshin this week or not?"
-"Now...count up your crimes"
-Kamen Rider Kikaider. You know the form.
-"WATASHI KIITENAI!" (Also the endless debate on whether or not Aki is annoying or not.
-'Will Nazca be naked this week or not?"
-"Golgom! What are you up to this time?"
-"I AM AMAZON!"
-(In response to that
scene) "DID HE JUST RIP OFF THAT DUDE'S HEAD!?"
-"THE NEXT SUCKED!"
-Female Riders must be destroyed according to almighty Toei law.
-"I want something like Kuuga/Agito this year."
-"Where are the original actors?!!"
-Chuck Norris the Kamen Rider.
Anything else I'm missing?