An improve version of https://gist.github.com/BlackMac/1825401

ctags_autocomplete.py

# CTags based autocompletion plugin for Sublime Text 2
# You can add the file to the User Package in ~/Library/Application Support/Sublime Text 2/Packages and restart Sublime Text 2.
# generate the .tags file in your project root with "ctags -R -f .tags"
# Author nodtem66
# fork from: https://gist.github.com/BlackMac/1825401
 
import sublime, sublime_plugin, os
 
class AutocompleteAll(sublime_plugin.EventListener):
 
    def on_query_completions(self, view, prefix, locations):
        tags_path = view.window().folders()[0]+"/.tags"
        results=[]
        if (not view.window().folders() or not os.path.exists(tags_path)): #check if a project is open and the .tags file exists
            return results
        f=os.popen("awk \"tolower($1) ~ /^"+ prefix.lower() + "/ {++n;print $1;}\" " + tags_path) # grep tags from project directory .tags file
        for i in f.readlines():
            results.append([i.strip()])
        results = [(item,item) for sublist in results for item in sublist] #flatten
        results = list(set(results)) # make unique
        results.sort() # sort
        return results

How to use this script

1 Install https://github.com/SublimeText/CTags
2 Open Sublime Text > Preferences > Browse Packages...
3 Put this script to that folder.

Requirement for Window

• Binary AWK from http://gnuwin32.sourceforge.net/packages/gawk.htm
  open zip and put it in somewhere included in %PATH%
• Test AWK; open cmd type awk if the system found awk you'll see the list of options

Test

• If did not have .tags, build it with Ctrl-T Ctrl-R
• Type something and use Ctrl-Space to see all autocompletes

So now use original Sublime/CTags.
It's already have autocomplete with the original script.
However, It's didn't work because you must have awk and ctagsplugin.py code has a bug about window command line.