Steam has The Binding of Isaac on sale for $1.24 (save 75% off). They also have the DLC Wrath of the Lamb on sale for $0.75 (75% off).

This is a daily deal on Steam and valid for today only.

Game Features

• Randomly generated dungeons, items enemies and bosses, you never play the same game twice.
• Over 100 unique items that not only give you powers but visually change your character.
• 50+ enemy types each with the ability to become “special” making them extra deadly but they also drop better loot.
• Over 20 bosses.
• 4 full chapters spanning 8 levels
• 3+ unlockable classes
• Multiple endings
• Tons of unlockable items, enemies, bosses and more.

All prices on Steam are in US dollars and exclude tax. You will need to install the Steam client in order to play the game and will need a free account.