Soviet Conscripts in Command & Conquer: Red Alert 3. They are quite enthusiastic and happy regardless of the fact that they are cannon-fodder par excellence; they'll shout "Field promotion, here I come!" as you order them to attack overwhelming enemy forces, and their first reaction to being ordered to garrison a building is to ask whether it's got TV.
The Aoi twins are probably the best example of the uke character archetype — they're young, energetic boys who wear clips in their long-ish hair and often wear costumes with a more feminine/androgynous feel. However, Yuuta is a bit of a downplayed example as he is the responsible sibling and can actually be pretty moody beneath the genki facade.
Mitsuru is another first-year example, a loud simple-minded Cheerful Child who runs everywhere (Dash, dash~).
Subaru is a touch older but his constant quest to find fun things, impulsiveness, and slight Cloud Cuckoo Lander tendencies definitely have him fitting this as well.
Contrast Madara — another extremely excitable character who loves running, but atypically, he's a third-year and is actually the tallest member of the entire cast, not to mention being something of an Anti-Hero who can be quite ruthless behind his giant grin.
And then consider Chiaki, who is also a third-year, but has such a childish love for Tokusatsu and such an earnest, naive nature that his energy level has him fitting perfectly into this trope again despite being part of the older third of the cast.
EXTRAPOWER: Attack of Darkforce has Melfa, the yellow Hikari Warrior. Small and adorable and he knows it, so he can get away with being a bit of a brat with the green Hikari Warrior Rakione.
Final Fantasy V: Bartz is the first protagonist to start a trend of cheerful heroes throughout the series.
Zack Fair, the protagonist in the Final Fantasy VII prequel Crisis Core, is enthusiastic, bouncy, and friendly to the point that people start sticking him with the nickname "puppy".
Zell, whose character introduction is literally him back-flipping into the room. He apparently used to zoom down the hallways on a hovering skateboard and has been known to throw really aggressive tantrums when the cafeteria is out of hot dogs. Adding to the effect, he also talks like he's Pretty Fly for a White Guy.
Laguna was incredibly energetic and always eager to do things and help others. Deconstructed somewhat in that others consider his acts of passion foolish at best. Ironically enough, Squall ends up being a brooding and stoic introvert who even considers his own father a moron on the first flashback.
Final Fantasy IX: Zidane overlaps with The Casanova. His genki side really comes out whenever he's trying to woo the princess. It's no surprise that Eiko (mentioned above) develops a crush on him.
Final Fantasy X: Tidus certainly fits. Our first proper impression of him is him enthusiastically signing autographs for his fans and he manages to shock all the people of Spira with his attitude. Lulu remarks that he "really do[es] come from a world where there is no Sin" after having experienced a few weeks with him. Surprise surprise, he and Rikku (mentioned above) are Like Brother and Sister.
Final Fantasy X-2 has Gippal; whose theme is an energetic guitar riff, he's endlessly bright and cheery and doesn't seem to have a sense of personal boundaries. He has Ship Tease with — you guessed it — Rikku. His English voice actor Rick Gomez is one in real life too.
Final Fantasy XII: Vaan fills in this spot alongside Penelo in an otherwise very no-nonsense group. His enthusiasm is driven by his desire to become a Sky Pirate, and he's easily the most cheerful member of the group full of brooders.
Snow Villiers from Final Fantasy XIII is not a little boy at all — in fact, he's a positively huge rough-and-tumble looking guy — but he's got the personality pretty much down pat.
Final Fantasy XV: Prompto is easily the most energetic (and somewhat childish) out of his four friends, and is the photographer of the group and very easily smitten with women. Though the reason for this may be because he's not quite as skilled as a warrior compared to his companions and uses his cheery disposition to make up for it. Then it's later revealed through his own episode that he was meant to be one of Niflheim's super-soldiers cloned from a Mad Scientist before being spirited away to Lucis, and after fighting the said scientist decides he does not to live his life based on what others think of him.
Final Fantasy Dimensions: Sol, whose optimistic energy is impossible to dent. This is meant to contrast Nacht, who is stoic and tight-lipped.
Final Fantasy Type-0: Jack is perhaps the most energetic guy out of the entire Class 0.
Tidus (Final Fantasy X) feels like this. But it's a different play on this trope — he is not overly upbeat, but when you put him with the rest of the game's cast, he is a damn good machine of mood-lightening...unless you bring up his Father, in which case he becomes a Ball of Angry Angst. Zidane (Final Fantasy IX) counts as well, though he can occasionally get serious, and Bartz (Final Fantasy V) rounds out the trifecta of cheerful FF heroes in the 13th Cycle.
In the sequel, Vaan (Final Fantasy XII) ends up being pretty laid back about things, along with Laguna (Final Fantasy VIII). When he's in battle, however, he's extremely loud, self-confident, and boisterous.
Inazuma Eleven: Endou Mamoru is probably the happiest of the major heroes in the Raimon Academy and Inazuma Japan National. His happy personality and Heroic Spirit are what drive the team to victory. Moreover, he almost never angsts after the first game. His successor Matsukaze Tenma in Go! is no slouch either.
Kid Icarus: There's The Hero, Pit, to the point that even when the game gets dark and serious, he's incredibly difficult to take seriously.
Sora, the main hero of the series, can be relentlessly cheerful. He pretty much has to be to be able to keep up with a pair of classic Toons as his sidekicks.
Ventus from Birth by Sleep is just as adorable and cheerful as Sora, but in less of a "hyperactive puppy" kind of way and more of a down-to-earth, gently smiling fashion.
Louis from the original Left 4 Dead is another, perpetually optimistic flavor of keet, always hopeful, trying to keep the team's spirits up and looking at the bright side of things in the middle of a Zombie Apocalypse.
Cloud Cuckoo Lander Ellis from Left 4 Dead 2 is a Keet, though a toned-down, Southern version. Nick puts it best: "It's like a 4-year-old with guns. And a comprehensive grasp of every swear word in the English language."
The Legend of Zelda: The Wind Waker: Link is cheerful, upbeat, and downright silly at times, in contrast with his more serious characterization in most of the rest of the franchise. He can still go toe to toe with the baddest of the bad, but he was also once turned into a human pancake.
Conrad Verner is a hyperactive, hyperenthusiastic Fanboy who keeps trying to impress Shepard. If you're not careful in dealing with him, his enthusiasm can get him killed.
This is also pretty much the hat of the Salarians. Their absurdly fast metabolism forces them to be this and it's also the cause for their very short life span of 30-40 years. Mordin Solus is absurdly old at about 50 but is no less slower from age; in fact he's able still able to recite a line from the Major-General's Song perfectly from memory. He does this twice in the series, once on the Normandy 2 and once at his death.
There are plenty of examples of this in the MySims games, but Buddy is the most prominent, being a Cloud Cuckoolander who acts as the player's sidekick in some of the games.
Gregg from Night in the Woods. He cheerfully screams most of his lines, seemingly can't keep still and is super excited about everything that's hapenning.
"Let's do some criiiimes!"
Teddie from Persona 4. Tiny, loud, hyper, cheerful and the instigator of most of the homosexual things in the game.
More so than his anime counterpart, Barry/Pearl/Damion from Pokémon Diamond, Pearl, and Platinum He's always dashing everywhere he goes, frequently crashing into people, and seems to have No Indoor Voice. It turns out his father's the same way.
Hau, the main rival from the seventhgeneration games also fits. He's very cheerful and enthusiastic, constantly jumping for joy even after losing battles. Like Barry, it's rare to see him walking rather than running.
The Sega rhythm game Samba de Amigo gives us the title character, Amigo, who is a cute maraca-playing monkey who is absolutely nuts about doing what he loves. Interestingly, unlike most Keets, he doesn't talk much, at least outside of his own gamenote the volleyball minigame in the Wii version of Samba De Amigo does have Amigo speaking through speech bubbles, implying that he might be able to talk; he mostly just makes maraca noises instead.
Charmy Bee from Sonic The Hedgehog is often energetic, playful, and very scatterbrained.
Star Wars: The Old Republic The Smuggler's first companion, Corso Riggs, is a cheerfully enthusiastic Gun Nut and the party's ranged tank. Excitable, a bit naive, and you could fit his sense of self-preservation in a bottle cap.
In Vampire: The Masquerade - Bloodlines, Knox Harrington stands out in the World of Darkness by being ridiculously cheerful and enthusiastic, even about being poached by a vampire to become its blood-bonded servant. He also happens to be an ex-bounty hunter and quite good at Obfuscating Stupidity.
Wild ARMs gives us Zed; a Large Ham and Ineffectual Sympathetic Villain who acts like he's the coolest guy around. His entrance in Volcannon Trap has him burst through a wall and zoom into the room like a superhero.
