Sublime Text is very lightweight by default. Customization occurs on the fly thanks to Package Control.

Multiple cursors and column selection allows for versatile ways of editing.
ctrl + d will select the current word and each time the command is repeated, it adds the next occurrence of the word to the selection.
ctrl + click or middle-mouse click will place another cursor in the place that's clicked. Cursors can then be controlled together. This also permits selecting vertically.
ctrl + shift + l will place a cursor on every highlighted line.

Sublime Text uses TextMate's syntax declaration files to support new languages, it has all its menus and keybindings generated from JSON files, and it can be scripted to add new features using Python.
If Sublime Text doesn't support a desired language or feature, it's usually not long before someone implements it themselves - examples include the plugin package manager and the 'open in browser' command.

Sublime Text has a minimap on the side that provides a top-down view of the file and keyboard shortcuts for most actions. It also supports a large number of languages and general text editing features out of the box.