Alfred is a launcher for OS X. It's primarily used as a replacement for Spotlight. For alternatives see here.
Alfred is a productivity tool for OSX that provides numerous improvements to the operating system.
Ranked in these QuestionsQuestion Ranking
Pro Versatile search
Quickly search for files, applications and web services from the same input.
Pro Can create custom automated workflows
Allows the creation of automated workflows by connecting keywords, hotkeys and actions together without writing code.
Pro Built-in calculator
Alfred is able to handle simple mathematical commands and more extensive expressions alike. Pressing Enter copies the result to the clipboard.
Pro Full keyboard controls
You can do everything using just the keyboard.
Pro Entry of everything
Pro Allows theming
Alfred allows adjusting colors, fonts, sizes and more to create new themes.
Pro Clipboard history
Alfred offers a clipboard with an extensive history for quick access to your copied text, images and links.
Pro Integrates with 1Password
Alfred allows getting secure and fast access to your 1Password 1Click bookmarks.
Pro Lightweight and smooth
Alfred is a lightweight application for OS X and runs smoothly, even on older devices.
Pro Offers both a free version and a paid version available
The paid version is more customizable, but the free version is still very powerful.
Con Many features require the $25 powerpack add-on
Features like custom workflows, clipboard history, 1Password integrations and others require the powerpack add-on.