if something is cool, awesome, amazing, exciting, etc.

Meta-meme is a meme which transcends all other memes. It's ironic in content as well as form. At first it usually doesn't make much sense, but that's only because it's memeing itself. Once you understand its memetics, you understand the whole meme culture.
Usually very distorted, misspellt and shiny, a meta-meme combines elements of different mostly ironic or pre-ironic memes.

Someone who only picks or uses top-tier or "in the meta" characters in a game. This can include hero picks in mobas, deck lists in card games, or a specific setup for a character class in an RPG.

A top tier character appearing in Brawl. Due to his all-around flurry attack and his major recovery,
he was a top tier character that basically was generally used by many in Brawl tournaments. His victory theme was burned into most of us.

Someone who ONLY follows the meta(Most Effective Tactic Available)and doesn't try anything else apart from the ever-shifting meta regardless if its fun or not and thus are like a slave to the meta.

Beyond hip. The next phase in the History of Cool (time for John Leland to add a chapter to his book) Non-mainstream culture (and it's trends) will be heading to a more organic, fluid phase. Culture is taking a swing away from the the image conscious, cooler-than-thou attitude of the Hipster sect, moving into a cycle where simplicity, inner pursuits and brightness are the nexus.

Someone famous for being famous (or infamous), particularly in the entertainment industry. A meta-celebrity is a well known celebrity, who has not done anything particularly noteworthy to justify their Fame. The late Anna Nicole Smith and Paris Hilton are two contemporary examples. Meta-celebrities do not always orginate in the entertainment industry, but they nearly always gravitate to it, often as a last ditch effort to extend their "fifteen minutes" as their profile starts to wane.

See also Professional Celebrity, Famious for being famous.