Botcon 2013 will be June 27th-30th this year in San Diego, CA. This is a convention for the Transformers and bot fans. Just like the San Diego Comic Con, this convention also has exclusive collectibles, usually for the Transformers line. I am including the link to the official page, just in case anyone wants to see what it is all about, or even register for the show (would be a nice trip if you have the time and funds for it).
Botcon is one of those bigger conventions that some how not everyone has heard of, but I can tell you, the exclusives are often very collectible. But if you can't go, thanks to the internet, you will be able to get them from E-Bay, Amazon, or even from the Transformers Fan Club, I'm sure.