I'm looking for a way to build an EDH deck that makes sure my opponents have fun while playing against me. In other words I'm less concerned with winning than with doing fun/creative/interesting things with my deck. I want the group to say "Wow, that's cool". I've never tried to build a non-competitive deck that focuses on something other than winning. So what are some mechanics that would be considered fun by the opponents?
This isn't mechanics specific, but theming is a good way to go. Themes can be based on Magic blocks with poor synergy or underpowered mechanics, like Kamigawa block (which likely will just make people laugh), or themes can be pulled from outside of the game, like trying to make a Lion King themed deck (or something else you like). Themes limit your options while being interesting to watch, especially if other players know the theme. Half the fun of out of Magic themes is in players trying to guess how specific cards fit into the theme.
As an example, I'm currently working on an Apocolypse deck (not the block, the out of Magic concept). The commander will be Child of Alara, with the four horsemen of the apocalypse as Iroas, God of Victory (War), Mogis, God of Slaughter (Death), Phiraka, God of Affliction (Pestilence), and Phenax, God of Deception (Famine). After getting these five cards set, the next step of the deck was to find cards that included the name of the four horsemen, so things like Sudden Death and War Elemental. This doesn't quite fill up the deck, especially if you're avoided hated cards like Death Cloud, so the rest of the deck is made up of mechanics that fit the four horsemen's mechanics. This included some mill for Famine, like Glimpse the Unthinkable, and some extra sacrifice for Death like Cruel Edict.
What you'll notice is that this deck isn't very synergistic and it will play differently every game. Competitive decks are tuned to play identically every time even though you only have 1 of every card. The theming will take away that consistency and will be fun to watch. And generally, you're going to have to put a decent amount of thought into the cards in a theme deck to make sure you're staying on theme, so it's going to take as much thought to produce as a well-tuned competitive deck. This process has the added benefit of causing you to think about Magic in a way you wouldn't normally, and maybe you'll find some playstyle or set of interactions you hadn't ever done before.
I haven't played much EDH, but I can imagine that these kinds of decks are NOT fun:
- Mass land destruction
- Too many counter spells / mass destruction
- "You can't" decks. E.g. Thalia, Sphere of Safety, etc.
Now, you have to deal with opponents eventually, so here might be some cards that can swing the tides in your favor while being "cool"
- Ezuri Predation or Clone Legion to handle / fight opponents creatures with your own.
- Ridiculous red/black spells: Descent of Dragons, Ghastly Conscription, Whims of the Fates(might be controversial, likely highly entertaining), Worst Fears
- "Battlecruiser magic" mostly big, flashy spells/creatures (e.g. Hydra Broodmaster for a ridiculous number of tokens)
Or just play a theme deck that isn't too oppressive. Slivers might be a bit too strong. Elves/goblins/humans/zombies/angels/demons/giants/enchantments/soldiers/whatever.
Not sure if this is what your looking for but of course one way to make people happy is to play cards that help everybody, by letting players get mana, draw cards, or any other beneficial "each player" card.
Examples of cards that opponents may like: