Bow down to tha master!
I used to play, still do if my friends bust out their cards.
10k+ cards... been playing since I was in 5th grade, when Revised (3rd) edition came out.
A few of my favorite decks I have together right now --
Blue/Green STUFF.
Has about 12-13 lands in the 60 card deck, with several ways to get the first few turns with land drops on the board, where I procede to build card advantage/quality with cheap blue spells and a few of the fast creatures and mana-free counterspells such as Force of Will, Daze and Foil... Gush (return 2 islands to your hand: draw 2 cards) and Deep Analysis (FLashback, UI: pay 3 life, draw 2 cards) are crucial for keeping my hand full and my opponent on their heels
Quiron Dryad G1
1/1
Whenever you play a blue, red, black or white spell, put a +1/+1 counter on Quiron Dryad
Once I get one of these badboys down with several ways of defending him, or at least delaying the opponent mounting a decent defense, it's usually game over. One of my most challenging decks to play and a lot of fun, when you're opponent tries something you have time to play about 4-5 spells to find a counterspell to solve your problem...
The other deck I have that I really enjoy is like the antithesis of my usual Blue or Red based decks I'm well known for among my circle of friends... just straight green beatdown!
This one only has 16 or so lands in the 60 card deck, 10 of which are actual forrests, with some sacrifice lands that let me look for more forrests, and 2 lands that have "Threshold: G, Tap and sacrifice: Target creature gets +3/+3 until end of turn".. with those, I have about 14 "Giant Growth" type cards in the deck.
What makes it so dangerous are the fast, BIG creatures for cheap cost, like:
Rogue Elephant
G 3/3
When Rogue Elephant comes into play, sacrifice a forrest.
Spectral Bears
G1 3/3
Does not untap during your untap phase if it attacked last turn. Untaps as normal if your opponent controls any black cards.
Skyshroud Ridgeback
G 2/3
Fading: 2 (During your upkeep, remove a fade counter. If you can't remove a fade counter, destroy this card, it cannot be regenerated.)
And the big beat stick to break tiebreakers - my personal preference over the beastly Blastoderm:
Phantom Centuar
GG2 3/0
Comes into play with 3 +1 / +1 counters.
If damage would be dealt to Phantom Centuar, prevent that damage and remove a +1/+1 counter instead.
With Elvish Spirit Guides...
G2 2/2
If Evlish Spirit Guide is in your hand, you may remove it from the game. if you do, add G to your mana pool.
4th Turn kills with this deck aren't uncommon, even with resistance offered. Nice deck once you play mindgames with your opponent while he tries to calculate how much damage he can take based on how many Giant Growth effects you have in your hand... I often will hold back lands just to give the illusion I have something when I don't!
I'll post more decks in another post if anybody cares.

I love talking about MTG. I don't want to spend any more money ever on it though...