've always liked the idea of colorless Commander decks, and while browsing Commander lists on TCGplayer, I found a Karn, Silver Golem list made by a user named terry_suave. In order to harness the power of Karn as your Commander, you do have to give up colored spells of any kind, which is a big cost. Luckily, that cost is more than made up for by sweetness, as Karn opens the door for all sorts of cool interactions.
There are clearly too many combinations to list, but here are a few of my favorite ones:
Rings of Brighthearth + almost anything = value. There are a ton of ways to go infinite, but my favorite combos are the ones that are explicitly not infinite. It's so much more fun to just make a bunch of Lux Cannon counters or Phyrexian Processor tokens than to go off and win the game.
Temporal Aperture + Eldrazi (Ulamog, Kozilek, etc.). If you are lucky enough to flip an Eldrazi, you get the full benefit, which is awesome. There are also plenty of other very expensive spells, so even a "miss" might not be.
Darksteel Forge + Nevinyrral's Disk. This may not be the most amusing for your opponents, but getting to blow up the world every turn is powerful indeed.
Karn Liberated + seven mana. You may not know this, but Karn Liberated is one of my favorite cards, and just casting it is enough to make me happy.
Past the combos, this deck has enough huge monsters and powerful cards that I know I'd have a blast playing it. Accelerating into Myr Battlesphere or Steel Hellkite sounds awesome, and as long as you stay away from hitting the infinite combo space too hard, your opponents shouldn't feel it too necessary to kill you first.
terry_sauve's Karn, Silver Golem Commander
Commander - Karn, Silver Golem
Luis Scott-Vargas plays, writes, and makes videos about Magic. He has played on the Pro Tour for almost a decade, and between that and producing content for ChannelFireball, often has his hands full (of cards).