How many?

[Ekann1]

1.5 EDH, 3/4 Standard, 7 casual

[InfinitiveDivinity]

4 (Soon to be 5) EDH, 3 Modern, 2-ish Standard, and about 5 casual decks that I actually consider fun. I have a lot of old weird builds randomly inserted into piles that I stumble across from time to time.

[imFourth of Phils]

4 Legacy (im a {Sneak Attack} and {Show and Tell} avid

Sneak and Show
Sneak Big Red
Fun Sneak
Fun Show

2 modern

UG Infect
Geist Vat

1 EDH

Phage Commander

[Spencer Addington]

2 modern ({W}{R} soul sisters and RDW) and 3 casual (goblins, {W} exalted and {G} infect).

[Coffee Vampire]

1 Commander

That's it right now! I may start standard again once this silly devotion business decides to leave...

[lotrwk]

13 EDH, 8 of which are for newer players that haven't played commander and want to try it out.
4 standard
{Satyr fire dancer}
G/W midrange
R/U/G monsters
Naya control

3 modern
{Quest for the holy relic}
{Scape shift}
{Fist of suns}

[Juggalonoke]

Ok I feel as if I may have gone overboard myself with edh, I have 30 commander decks (soon to be 34), 12 casual decks, 1 modern goblin deck, and been working on a legacy deck. Haven't played standard sense gatecrash dropped in stores.

[Sparkle Ninja]

Ok I feel as if I may have gone overboard myself with edh, I have 30 commander decks (soon to be 34), 12 casual decks, 1 modern goblin deck, and been working on a legacy deck. Haven't played standard sense gatecrash dropped in stores.

Holy crap

[DirtyMustachio]

2 casual
2 edh
4 standard
1 modern working on more

All pseudo competitive

[Rass]

Well two casual decks  a spirit and a kiln fiend deck. Every event deck and duel deck (haven't played all the duel decks because they get owned a lot unless playing other duel decks.) wish I had more time to make some decks but most of my collection is in storage until I get another house (long story). But the event decks are fun and somewhat competitive.

[MacheteMable]

13 EDH, 8 of which are for newer players that haven't played commander and want to try it out.
4 standard
{Satyr fire dancer}
G/W midrange
R/U/G monsters
Naya control

3 modern
{Quest for the holy relic}
{Scape shift}
{Fist of suns}

Yay I'm not the only one with an insane amount of edh deckness

[Sparkle Ninja]

2 casual
2 edh
4 standard
1 modern working on more

All pseudo competitive

I'll play a pseudo competive EDH game with yoy

[Teysa karlov]

2 modern. (8 rack and mono black vampires)
1 standrd. (Orzhov midrange)
2 EDH (teysa orzhov scion and  Nekusar, the Mindrazer)
1 casual ( burn)

[Juggalonoke]

Ok I feel as if I may have gone overboard myself with edh, I have 30 commander decks (soon to be 34), 12 casual decks, 1 modern goblin deck, and been working on a legacy deck. Haven't played standard sense gatecrash dropped in stores.

How to kill time.  Get 9 of your friends.  Each person grabs 3 decks.  Play until you have a winner with nothing that says "you win". That'd be cheating everyone out of 50 hours of magic. 

Now I wish I had 6 other friends like that who played magic whom I'd be willing to spend that much time with lmao

[Mr_Fahrenheit]

I have two complete and competitive standard decks, plus a third that I'm in the process of rebuilding after I had to rape it for its mana base. I'm working on 3 modern decks, all nearly complete plus one legacy. I also have 3 pauper decks and one commander deck as I like those alternate formats. There is also anywhere between 4 and 8 casual decks at any given time as i play a lot of casual multiplayer. For that reason they are not very competitive in anything but casual multiplayer lol