If you're a Zombies fan, specifically a Black Ops Zombies fan, chances are that you've heard of the Ronald Raygun, the name of which is clearly a play on former US president Ronald Reagan, who served from 1981 to 1989.
Ronald Reagan also appears in the Black Ops Cold War campaign as the United States president. It makes sense, as he was the president during the real-life Cold War era. After all, Call of Duty games are known for non-fictitious characters and being heavily inspired by real war events.
There is a brand new easter egg added in the Outbreak mode which not only guarantees a Raygun, but is also very rare to come across. Treyarch has added a unique zombie with a pink-haired mohawk in the game named Ronald Raygun.
Ronald Raygun has been a meme for quite some time in the Zombies community with the last name "Reagan" sounding very similar to "Raygun", hence the play on the words resulting in Ronald Raygun.
If you kill this particular zombie in the Outbreak mode, you are pretty much guaranteed a Raygun drop, which you can use for the rest of your Outbreak game.
The chances of Ronald Raygun zombie spawning are meagre, and there is no particular method to increase the chances for it to spawn. You need to pay attention to all the hordes of zombies and keep an eye out for the one having a pink-haired mohawk if you want that free Raygun. It is certainly not worth the effort to go around and look for this zombie specifically, as the zombie is very rare.
The following video showcases the Ronald Raygun zombie in the Golova region.
You have better chances of finding the Raygun from a Trial Computer than to find the Ronald Raygun. Still, it is pretty cool to see that the developers pay attention to the zombies' community and acknowledge their memes.