Here's a casual deck I call Black Burn Cycle. I haven't bought any cards after Ravnica, so please don't suggest anything from Ravnica or newer.

23 creatures

4 Maggot Carrier
4 Bile Urchin
4 Nezumi Cutthroat
4 Ashen-Skin Zubera
3 Thief of Hope
3 Deathknell Kami
1 Seizan, Perverter of Truth

15 other

4 Dark Banishing
4 Midnight Covenant
3 Death Denied
2 Kiku's Shadow
2 Devouring Greed

22 Land
20 Swamp
1 Tomb of Urami
1 Cabal Coffers

The basic idea is to kill the opponent slowly with Maggot Carrier, Thief of Hope, Nezumi Cutthroat, and Bile Urchin. After 2-3 turns, the deck picks up the pace and does more damage with Nezumi Cutthroat/Deathknell Kami and Midnight Covenant. If I need something to finish the game off, I have Seizan, Tomb of Urami, and Devouring Greed.

Ths deck actually wins games pretty quickly, sometimes against tournament-competitive decks.