This isn’t the only tool that mines Google Autocomplete. There’s also, but this tool restricts results to ~700 keywords (more are available for “pro” members). Infinite Suggest is another alternative, but despite the name, I’ve found that it still doesn’t find anywhere near the number of keywords that Keyword Shitter finds. And there are tons of other Google Autocomplete miners too. Just Google “google auto suggest tool” for more. There’s also this tool from SEOChat which mines autocomplete suggestions from Google, Bing, Amazon, and YouTube.
While this one isn’t necessarily a keyword research tool, it will give you valuable insight into how the keywords you’ve been optimizing for so far are actually performing for you. You might realize that you could start ranking for more keywords with more difficult competition, for example, or that only keywords on certain subjects are working for you.
WordStream's Negative Keyword Tool reduces wasteful PPC spending and improves ROI by preventing your AdWords PPC ads from showing on irrelevant searches. Enter a keyword to get a list of negative keyword suggestions. Then select the ones that aren't relevant to your campaigns and export the results for use in your AdWords account. As a result, your ads will be more relevant to searchers, grab a much more targeted audience and reduce your overall ad spend.

In a nutshell, Long Tail Pro helps you quickly find keywords in bulk based on a seed keyword that you input.  In addition to returning hundreds of related keywords, the tool also shows search volume (monthly search volume), advertiser bid, number of words, rank value, and my favorite Keyword Competitiveness (helps you judge the competition and keyword difficulty).