It is always a very fun process of developing combos (or at least I think it is), but to come up with the best combo for multiplayer? This is a very challenging deli mea. There are several principles that need to be recognized if you want to play multiplayer using a combo deck. These principles are:

1. The combo must be fast.
This requires that your combo is made of the fewest possible cards. Good multiplayer combo decks usually only need two to three pieces for their combo. Sure, that seven-card may be nice - but if the fastest it can go off is turn 10, you either need to improve its ability to control the game, or you need to find a new combo.

2. The combo must be able to kill multiple opponents.
This is not a very hard requirement to fulfill with some combo decks, like the Wirewood Channeler/Pemmin's Aura combo generates near-infinite mana; this can then be funneled into creatures such as Kamahl, Fist of Krosa or Nemata, Grove Guardian, which would then allow you to kill everyone through a massive attack. Usually, combos that produce an arbitrarily large amount of mana are good at killing multiple opponents. Decks that would not be good in multiplayer would be ones like Mean Deck Tendrils or Goblin Charbelcher, as they only focus on one opponent - but you knew that, right?

3. The combo must be able to win.
This may seem silly that I bring it up, but it is important. "What combo deck doesn't win?" you may ask, and the answer is: "The kind focused on not losing, that's what."

An example of a combo deck that doesn't just flat-out win is Life. Actually, life is not a very bad combo in multiplayer - but if your play group is anything like mine there is always someone who likes to win with Phage the Untouchable or Epic Struggle, so you would need to get a Test of Endurance rather quickly if you're playing Life. Of course, most combo decks are good at winning - but as previously stated, it must be able to win against multiple foes.

4. It must not be apparent that you're playing combo.
This should probably be the number one rule: If people can tell you're playing a combo deck, you will either need to go off seconds after they realize this fact or you will sputter and die. I have played the Staff of Domination + massive mana-generating creature deck, but I always have one problem - people can tell I'm playing combo. As soon as that happens, none of my creatures stick on the freakin' board. It is important not to attract attention to yourself, as there are many opponents - surviving one to two attacks may be workable, but surviving seven or eight is suicidal.

5. Plan B.
I'm not referring about Once More With Feeling or Sway of the Stars by this statement - I'm saying that it's wise for your deck to have a backup plan other than just comboing out. I bring this up because I've seen several occasions where Eradicate, Scour, Splinter, or Cranial Extraction has torn up a perfectly good combo and wasted it into a pile of smoldering ash. A good combo deck in multiplayer should not only be able to win with the combo, but win without it as well.

An example of a combo deck that can win without going off is the Staff of Domination combo; depending on the build, the deck can still win with creature beatdown.

*Extra* the deck wins in a fun, funny, or cool way.
It always is fun to play against a Combo deck that wins in a rather fun way. I personally would suggest a deck that I used to play that could make an abruptly large amount of dragon tokens - but that was a venerable combo and was easily disrupted.

I bring this up for a reason, though. How many of you have been killed by Stroke of Genius (and its Alpha brother, Braingeyser) or a Fireball? Braingeyser and Stroke of Genius are not only not fun to lose to, but make lousy finishers in multiplayer (they break rule number 2). Fireball, on the other hand, is good at killing multiple players and is a useful card to take out multiple creatures - but it's nowhere near as fun as losing to a billion dragons.

My friends always though it was cool that dragons were taking them down. I only bring this up because it makes the game more enjoyable for everyone, even for the guy who got mana screwed.

With all these elements in mind, there are a few combo decks that come to mind. One is the Myr Retriever/Disciple of the Vault/Ashnod's Altar combo, but I will dismiss this since it is technically four pieces and not three... and though the deck could potentially be built to win without the combo, I have yet to see one outlast green beatdown decks. I also will dismiss the Staff of Domination combos - not because it's bad, but due to the way my playgroup functions and the fact someone has already written about it.

The deck I believe that has one of the best combos for multiplayer is as follows:

Lands (24)
4 Great Furnace
4 Ancient Den
4 Darksteel Citadel
4 Glimmervoid
4 Battlefield Forge
4 Tendo Ice Bridge

Creatures (23)
3 Goblin Welder
4 Iron Myr
4 Gold Myr
3 Triskelion
4 Myr Enforcer
2 Myr Retriever
3 Flametongue Kavu

Other (13)
3 Myr Matrix
2 Mana Echoes
3 Fireball (or Rolling Thunder)
4 Golden Wish
1 Enlightened Tutor

+Tool Box

Most people look at the deck and dismiss it as a pile, but it really is quite effective. The deck's combo is one that some people already know about; Myr Matrix and Mana Echoes allow you to produce infinite mana. This mana may then either be spent on killing all your opponents and their creatures with a massive Fireball, or just producing a billion Myr; my group finds it funny to die by massive amounts of Myr.

The deck disguises itself as an artifact deck, so long as you don't lay down Mana Echoes too soon. The deck handles early assaults by churning out an early Triskelion, which will chump and shoot anything coming your way all day long. Goblin Welder also is very useful in turning your creatures into continual chumpers (and they also bring back Myr Matrices that you may have discarded). Myr Retriever serves a similar role as the Welder, but allows a continual stream of artifact recursion with a Welder.

Myr Enforcer serves as an earlier beater or defender and has the capability of being free, allowing you to tap out for Echoes if the Matrix is in play (or vice versa) and going off on that turn. The mana Myr are there to speed out the combo and to create the illusion of a Myr theme deck.

Flametongue Kavu is in the deck because - wait, why am I explaining him? All of you already know the strength of the Kavu, and that doesn't change for multiplayer; four damage and a strong attacker/blocker that is almost guaranteed to kill anything it engages in is always good.

Ironically, the least-popular wish, Golden Wish, is an important tool for getting your combo off the ground, or for fishing up an answer to a problem. Golden Wish is part of the reason I put in the Tendo Ice Bridges; the ability to search up enchantments of other colors can be handy when dealing with certain opponents. Examples include City of Solitude, Arcane Laboratory (though Rule of Law also works and is in color), or perhaps a Seal of Doom. Golden Wish allows you to also carry a toolbox, so you can fish up what you need when you need it. Golden Wish is also the reason I put only two Mana Echoes in the deck, as drawing multiples earlier on doesn't help.

The deck is, overall, a pretty good multiplayer deck. It can deal with a multitude of problems and is quite fun to play.

Tips On Playing The Deck.
The deck plays on the slower side and works more like an aggro/control-type deck before the combo goes off. It is often a bad idea to rush the combo, at least the Mana Echoes part of it. Myr Matrix will often help you hold off other decks, produce creatures, and it is very resistant to hate, though I would suggest being careful if your group plays Splinters.

Also, make sure you (or someone else) deal with the people who could be potential problems to your deck. Those people are the ones who can destroy/bounce all your tokens (Evacuation, Echoing Truth/Echoing Ruin/Echoing Decay, and Wrath of God, to name a few).

Always make sure you save your Kavus for creatures that can become quite troublesome to your game plans (like Meddling Mage, Goblin Welder, and Devout Witness). Fireballs are to be used as needed; do not be afraid of using Fireballs to take out opposing threats; you may want to Fireball your opponents when you get the combo off, but you may not live long enough to get the chance.

Trike and Goblin Welder work wonders for your defense and offense, but don't get too carried away with them; save the activations for when they are necessary, only taking down what you have to in order to protect yourself.

When Wishing with Golden Wish, don't automatically grab the missing piece of the combo - instead, pick what will help you survive or win at the present moment. If you can go off with the combo the turn you cast the Wish (or one turn afterward), go for it- but if you need to live, by all means save yourself.

Note that you don't always have to cast the Wish right away; sometimes it's best just to save it for the right occasion. (That's good advice for any card - T.F.)

As one final note, this deck is not supposed to be some great tournament winner - it's supposed to be fun! (You are playing multiplayer, right?)

Extra
I brought up earlier how I had a combo deck that made infinite dragon tokens - and while it doesn't win as often, I just wanted to share the combo. Mana Echoes is one of the combo pieces, the other two are Skyshroud Elf and Dragon Roost. The way this combo is sped out is through the use of Elves. Once the Echoes is in play, you usually need to play some elves and tap some others, using both the elves' mana and the Echoes mana. Once you have enough mana, just pump out dragons all the livelong day.