Greetings, LoL Wiki members! I know there are a ton of people doing these right now, but I firmly believe that I can make this post into solid reading material regardless of whether or not I happen to win something.
I used to play DotA in phases several years ago with about three different groups of friends at three separate eras of my life. I was never very good at the game, but it was by far the most interesting custom map stemming from a well-known RTS I'd ever played. Just over a year ago, at the recommendation of one of my DotA buddies, I got into Heroes of Newerth when it was still in its beta stages and still very much like DotA. After playing HoN religiously for several months, I eventually got fed up with the hostile nature of the community; I found myself hard-pressed to really enjoy a game that I wasn't playing with an entire group of personal friends. It was around this time that I was introduced to LoL by an old friend of mine from high school. He had been playing LoL since beta, was very talented at the game, and made it his business to teach me everything he knew, easing the transition from HoN to LoL for me along the way. Not long after I finally reached level 30, I came to discover that nearly all of my gamer friends had been playing LoL for a while or were just getting into the game, and ever since then I've had all the reason in the world to continue to stay involved in the rich experience LoL continues to provide.
There are a lot of champions in this game that I love to play and continuously come back to, but there is one champion in particular that I hold near and dear to my heart: Karma. I don't want to assume that this is a completely unique response, but I wouldn't be surprised if it was; Karma has to be one of the most quickly forgotten champions in the game, because seeing her in a game is incredibly rare. Part of the reason I love her so much is because of the fact that she's underused, misunderstood, and generally labeled as being a mediocre champion -- because people don't know what she's really capable of doing. But that's much more the short answer than the full story.
Karma is labeled as a "support" champion on the premise that she has a heal and a shield. However, both of these abilities double as AoE burst damage sources on top of their more support-oriented effects; most heal/shield abilities are solely dedicated to that single purpose. Furthermore, most well-known support champions (Janna, Taric, etc.) have reliable sources of CC and/or utility (Janna's Howling Gale and Monsoon, Taric's Dazzle, etc.); Karma has nothing of the sort, with Spirit Bond only serving as a haste/slow. More so even than Sona, Karma appears to benefit from AP more than any other support champion -- but by building heavy AP, her burst damage starts to escalate to incredible levels in the right hands. So while Karma hides under the guise of "support", she feels and plays much more like an AP carry that happens to also have a heal and a shield. And when you look at it from that angle, it seems potentially overpowered.
I've been playing fighting games competitively for several years now, and quick and precise execution is an essential requirement for being a part of that scene. This taken into consideration, Karma is my favorite champion because she is very difficult to master but absolutely devastating in trained hands (much like Orianna, only not quite as ridiculous). Quick and precise execution is required to make the most out of Karma's capabilities, and I always love challenging myself by playing complicated characters in competitive games. Even without superior execution, however, Karma is a unique champion in that by building for one role you can easily serve two: AP carry and support. She is powerful, she is versatile, she is awesome. There is far more to Karma than meets the eye, and when you see something in a champion that no one else seems to understand, that's how you know the champion calls to your desired play style, and that's how you turn a champion no one expected into something amazing. That's why Karma is my favorite champion.