THE BEST PLUGIN

IncrementSelectionCommand.py

# Sublime: Tools -> Developer -> New Plugin
# Preferences -> Key Bindings
# Default (OSX).sublime-keymap: { "keys": ["alt+1"], "command": "increment_selection" }

import sublime, sublime_plugin

class IncrementSelectionCommand(sublime_plugin.TextCommand):
	def run(self, edit):
		start_value = 1

		counter = 0
		for selection in self.view.sel():
			self.view.insert(edit, selection.begin(), str(start_value + counter))
			counter = counter + 1