Mana: (22)
4 Scrubland
4 Salt Flats
2 Reflecting Pool
2 Plains
5 Swamps
2 Thawing Glaciers
1 Sol Ring
1 Strip Mine
1 Wasteland

Creatures: (12)
4 White Knight
4 Paladin en-Vec
3 Duskrider Falcon
1 Cho-Manno, Revolutionary

Pestilence Fun: (10)
3 Pestilence
1 The Abyss
3 Deathlace
2 Pariah
1 COP: Black

Support: (14)
3 Enlightened Tutor
1 Demonic Tutor
4 Swords to Plowshares
3 Cursed Scroll
1 Balance
2 Aura of Silence

STRATEGY:

1) Land and a Pestilence Deck's fundamental problem
A Pestilence deck logically has black and white. However, the deck needs double-colored mana costs early because the best decks have Pestilence and a black mana base to power it and white weenies with protection from black, the best of white have double-white.
I solve this problem with 10 dual lands. Salt Flats is tolerable since this is not a speed deck and it has no one-mana drops. Tithe can be used to support Scrublands, but there is a danger of drawing no white mana. I used Thawing Glaciers to support Pestilence in the mid-game and as a last resort to drawing the correct color mana in the first few turns. (Land Tax can also be used instead of Glaciers, but Cursed Scroll is important to this deck.)
Note that Dark Rituals were not used. Only Pestilence and Abyss actually benefit from these, so they were not used. (Because there are no Dark Rituals, Yawgmoth's Will was also not used.)

2) Creatures
Pestilence's mana problem can be offset by using high-toughness or regenerating black creatures, but white weenies with protection from black are really the most efficient alternatives. The mana problem, however, prevents the use of pump-knights (Order of Leitbur and Order of the White Shield) since there is not enough white mana to make full use of these.
White Knight is the first-pick. Duskrider Falcon is a flyer, also for 2 mana. Paladin en-Vec gives the deck an auto-win option against red (with Pariah) and red/black. Other good picks include Death Speakers and Voice of Grace, but these are less efficient than the choices listed. Warrior en-Kor is usable in a deck with a good number of protection from black creatures and is a better option with Pariah when facing a bolt-heavy red deck.
Cho-Manno is, of course, the mascot of this fun deck.
The strategy is simple: this is not a white weenie rush deck. Cast your creatures first and use them to block (if there is anything to block). 8 first-striking knights are good for this. Pestilence (or Abyss) will soon appear to break the ground stalemate, and your blockers become win options. Note that if one does not have enough black mana to kill a high-toughness attacker, one can use Pestilence to deal some damage and let first strike damage finish.

3) Pestilence fun components
Pestilence was used over the cheaper Ice Age Withering Wisps because of the mana problem and because Pestilence is intended as a control card and finisher, so the additional one mana is a good tradeoff for the overall stability of the deck.
Pestilence and Abyss should be played after some creature defense is out and the theme centers around these two cards. Normally, COP: Black is used with Pestilence, but this requires 2 mana per point of damage. Unless one is facing a deck with heavy creature-elimination, Pariah provides a much better alternative and allows a player to dump all of one's black mana into Pestilence during the opponent's end-of-turn. This allows for a faster finish once Pestilence is played, and saves the Pestilence player the trouble of worrying about having a bolt player finish him off after both players' life totals dip due to Pestilence. Again, note that Pariah on Cho-Manno or Paladin en-Vec is almost an auto-win against red.
One COP: Black is still included for certain situations where it becomes more useful than Pariah, or against a black deck.
Deathlace is the #1 "fun" card for this casual deck. It looks like a joke but is amazingly flexible. It can save a blocker early on by suddenly turning the attacker black before damage is assigned. Lacing permanents also goes well with COP: Black and foils colorless damage sources such as Masticore and Cursed Scroll (note that Masticore regenerates vs Pestilence and Cursed Scroll is unaffected by Pestilence). Among the many other uses, the most fun would be lacing a large Fireball and watching it dissipate harmlessly off a Pariah or COP: Black.

4) Enlightened Tutor and other support cards
Note that this deck is meant to run off Enlightened Tutor. Having 3 Enlightened Tutors (and the Demonic Tutor, of course) almost means that there are three additional copies of each key enchantment in the deck (Editor's Note: Since the time of this writing, Enlightened Tutor has made the Type I restricted list). This provides great flexibility as it allows the needed card to be drawn the next turn (note that Aura of Silence was selected over Disenchant for this purpose and Cursed Scroll and Abyss can also be picked up). It also allows using just one copy of a card that may be key against one deck but useless against another, or enchantments that are useless in multiples (like Pestilence and Pariah).
The other cards, especially Balance, are self-explanatory. (Balance is fun all in itself!)
The choice of creature kill, perhaps, deserves a note, however. Swords to Plowshares was chosen because the other black spells (Contagion, Terror, Dark Banishing, Vendetta, Snuff Out, Diabolic Edict) are unnecessary due to Pestilence (Edict is useless because all untargettable creatures will die to Pestilence). What is needed is a pinpoint spell that can remove other protection from black creatures, should this deck come up against a White Weenie. Swords to Plowshares also provides a bonus against recursion decks, especially Oath of Druids. Cursed Scroll is in for the same reason, but it provides another win option in a deck with low-casting cost cards.