There are several Autobots whose names start with O but there’s only one real choice for this: Optimus Prime, the greatest Transformer of them all. It’s not even close in that regard, despite how much I might like other Transformers like Jetfire or Grapple.
In third grade we were supposed to write about a hero we admired; I ended up writing about Thomas Jefferson but really I would have picked Optimus Prime. I mean he’s everything you want in a hero: strong, brave, wise, kind, generous, and he had that great John Wayne voice provided by the awesome Peter Cullen. It’s safe to say Optimus Prime would be the best leader we could hope for in our modern world, even if he is a dictator in the traditional sense that he doesn’t command the Autobots through any democratic mechanism. His file card motto “Freedom is the right of all sentient beings” should be the mantra of all anti-Trump supporters.
Like Megatron, though, the original toy is kind of flimsy and puny. It was made of die-cast metal for the most part, which was pretty cool but he wasn’t actually all that big or bulky. He looked far more impressive on TV screens. A fun fact about his toy is that Hasbro (as they’re prone to do) repainted Optimus Prime white to use as the cab for the Ultra Magnus toy in the third series.
Optimus was the Autobot leader in the first two seasons of the TV series. In one episode the Aerialbots go back in time on Cybertron and meet a young bot named Orion Pax, who gets shot and it’s revealed that he was rebuilt into Optimus Prime, who became the leader of the Autobots and eventually led them to Earth on “the Ark” to search for new energy supplies. But the Decepticons intercepted them, the ship crashed, and for millions of years they were in suspended animation until being revived in the “present day” of the mid-1980s.
Besides losing my beloved Pound Puppy in Florida, one of the most traumatic memories from my childhood was watching the scene in the 1986 movie where Optimus Prime dies. It was like Kennedy being assassinated was for older people; here’s your hero dying right before your eyes! Such a thing doesn’t seem possible when you’re 8. And really up to that point Optimus had been shot and even disassembled and he always survived, so why would he die now?
Apparently I wasn’t the only one traumatized by this because by the end of the third season of the TV show, Hasbro had to change course and bring Optimus Prime back. First in one episode the evil Quintessons revived Optimus Prime to use him against the Autobots; he sacrificed himself to save the Autobots and seemingly destroy the Quintessons. But then the next episodes were “The Return of Optimus Prime” where a human ship finds Optimus. An evil scientist hopes to use him as bait to infect the Autobots with alien spores that are highly contagious and cause massive levels of hate and aggression. Rodimus Prime had directed Sky Lynx to pick up a Quintesson to revive Optimus Prime, and so he does and so Optimus Prime returns to life. By then the plague has spread to even Rodimus Prime and Optimus fights him for the Matrix before curing the plague by opening the Matrix.
In the Rebirth miniseries Optimus Prime is back in charge of the Autobots, but it would be a whole year yet until Hasbro actually made a new Optimus Prime toy. This was the Powermaster Optimus Prime toy where a little guy attached to his grill (the truck’s grill not his teeth) as an engine booster. Unlike the original toy, the trailer actually became armor for the cab, though you could still use the cab as a separate robot and trailer as a battle station if you wanted, but who would? Though he was all plastic now, Optimus was larger and more powerful-looking, more in line with his TV counterpart. There was an “Action Master” version a couple of years later where Optimus didn’t transform, just his truck part did. The original toy was reissued in the Generation 2 series and there were a couple of new versions of Optimus as well.
In the Beast Wars series the leader of the heroic Maximals is named Optimus Primal. As we learn later he’s not actually Optimus Prime, but his head looks the same, at least for the original toy. Optimus Primal turned into a gorilla that was a pretty neat toy. Later he had a new version that turned into a robotic gorilla and plane and a couple other things maybe.
Eventually the actual Optimus Prime returned in the later animated series. There have been many versions of him, though they usually are either semi-trucks or fire trucks.
Optimus Prime was again leader of the Autobots in the 2007 live action movie. In a nod to fans, Peter Cullen returned to voice the character and has continued to do so for all five movies. Instead of a flat-fronted truck the movie Optimus is a truck with a longer front end. In the fourth movie he disguised himself as a flat-fronted truck that looked more like the Ultra Magnus version since I think it was white, but eventually he turned back into the other kind of truck. From the trailers in the fifth movie Optimus turns evil—at least for a little while.
The original version of Optimus Prime in Transformers Prime is based on the movie version. It even does the thing where he has a normal mouth most of the time but in battle covers the mouth. I think the normal mouth and eyebrows looks a little weird. In the start of the second season Optimus lost his memory and thought he was his younger self Orion Pax and even joined the Decepticons before realizing they were evil. Near the end of the season he got a giant sword called the "Star Saber" that broke an episode later but was later fixed. At the start of the third season he was nearly killed but rebuilt in a bulkier body with a Gatling gun and flying mode similar to the one he gained at the end of the second movie. In Robots in Disguise he's dead, though probably not really.
In the Marvel comics Optimus Prime led the Autobots in the first four issues before they were all knocked out by Shockwave. While the other Autobots were in storage, Shockwave decapitated Prime until he was eventually rescued. Another traumatic childhood moment was in issue #24 when Optimus Prime was blown up after disqualifying himself in a video game tournament versus Megatron because he had inadvertently killed some of the little lemming people on the screen. Which was pretty fucking stupid, but whatever. He came back in issue #42 as a Powermaster and remained that way until Issue #75 when he died opening the Matrix to destroy Unicron. But of course he wasn’t dead! His consciousness lived on in the Nebulon dude who transformed into his engine booster and in issue #80 he dramatically returned.
The IDW miniseries Autocracy provides an origin story for how tough cop Orion Pax was nearly killed by Megatron, found the Matrix, and then united Cybertron against the Decepticons. After the war ended, Optimus gave up leadership of the Autobots and even for a time went back to Orion Pax until the conclusion of the Dark Cybertron story.
In my fanfic novel Transformers: Xenophobia, Optimus Prime makes a similar decision after the war to quit leading the Autobots. He takes a shuttle and is assigned a bodyguard, who is Jetfire's secret daughter, to explore uncharted space. Eventually he runs into Decepticons and his bodyguard saves him but is captured in the process. She meets her "mother", a Decepticon double-agent. Meanwhile Optimus goes back to Cybertron, which has chosen an unstable Hot Rod as its new leader--sort of a preview of the 2016 election!
Whew, that’s a lot of stuff isn’t it?
By comparison Octane is far less interesting. He was a triple-changer who turned from a robot into a fuel tanker truck or a jumbo jet. That would be pretty useful for delivering fuel, right? From his file card, he was more interested in making money than really being part of either side of the Cybertronian conflict.
In the third season of the TV show Octane helps the giant Trypticon recover from his injuries in the fight against Metroplex. He does this by essentially taking over a small desert country not unlike Libya until the rest of the Decepticons show up to seize power from him and then the Autobots drive them off. He became a target of the Decepticons for his apparent treachery and with the help of the Autobot Sandstorm survived a few assassination attempts.
That’s pretty much all the interesting stuff I can remember about him. I don’t think he really shows up anywhere else. Too bad for him. There is at least another toy that's about the same but called Tankor, so that's something.