Have you heard about Commander (colloquially; Elder Dragon Highlander)?
It's a pretty cool format.
You pick a legendary creature, and then you build a deck around that creature. Seems simple enough, but the format has a couple of caveats that help distinguish it from most other preconstructed formats.
1. The decks have 100 cards. Not 100 minimum, not 100 maximum. 100
2. The decks are singleton, meaning no two cards other than basic lands can share a name.
3. All of the cards have to share your general's color identity, which is all of the colors in its casting cost or any color symbols in its textbox.
4. Each player starts with 40 life.
All of these details combine to make Commander a slower, haymaker driven format. A lot of players lock to the format because they only need one card as opposed to the usual four-ofs in most other formats, and the format is slow enough to allow players to reliably cast big splashy spells that are too expensive to be reliable in other formats.
I heard about the format shortly after I started playing Magic (around the time Shards of Alara came out), but due to my legendary laziness, I didn't get around to building my own deck until this past summer.
As the article title may clue you in, I chose a personal favorite of mine and one of the first legendary creatures I ever saw; Mayael the Anima.
Something that has endeared me to Mayael is that attacking with creatures is generally less practical in the format that going off with some one hit kill combos, so Mayael tends to be less reliant on pricey format staples than other strategies.
Nonetheless, the format isn't nearly as widespread as say, standard, so a fear of mine is that even with the singleton nature of the format, that playing the same strategy over and over will get old.
So I've started using an interesting deckbuilding exercise I first heard about on Commandercast.
It was in regards to a Zur the Enchanter deck, but the strategy translates well to what I'm doing.
Basically, Zur has a well-earned reputation as a "that guy" deck ("that guy" translating to "you dirty rotten motherf-") so to make things more interesting, the pilot would choose his enchantments at random before each game. He had a pile of assorted enchantments he favored, and he would pick a bunch of them at random and shuffled them into his deck before each game.
Some games he would "go off" and just destroy everyone, others he would play cutesy, inoffensive stuff like Pacifism. There was no way to tell!
So, as you can guess, replace "enchantments with converted mana cost 3 or less" with "creatures with power 5 or greater" and that';s basically what I started doing, and its been a blast so far.
Some times I plop in a limited workhorse like Archangel, other games something oppressive like Iona, Shield of Emeria would come out to play.
If you play EDH and you find yourself getting bored with your deck, I recommend you to try this strategy out!