I've been promising this for a while now, and I finally will make good on that promise. This is a list for my "Big Highlander", a 250-card, 5 color monstrosity of a deck. It's a blast to play, though, lemme tell ya!
There's no real obvious theme - it's basically a 5-color "good stuff" deck, but there is at least a unity and cohesiveness to what I consider "good stuff". I don't run countermagic, even really good ones like Force of Will or Cryptic Command. I primarily tend to focus on good recursion, draw, and other card-advantage generators. Broken stuff like Survival of the Fittest and Recurring Nightmare star along side "fun" stuff like Maelstrom Nexus and Wild Pair, but all are capable of providing me with overwhelming card advantage or board presence.
Because the deck is so hard to parse by simply looking at a list, I'm uploading a spreadsheet to Google Docs, so that you can sort the list and play with it a bit to see what the deck holds.
Link to spreadsheet.
I really don't have too much to explain here - this deck has evolved over the years and has been lovingly crafted through extensive playing. Virtually every card in the deck is proven, and is undeniably worth it's slot. That being said, I have a huge stack of cards that have either been cut despite their being really good (to make room for new hotness such as Geth, etc.) or cards that have been battle-tested in EDH and are waiting their turn in the big highlander.
There's almost no wrong way to build this deck, but if you want to break into this format, just stick as close as possible to my list, and substitue similar effects where needed. Play a few games, then season to taste!