The Keyword Tool is similar to Übersuggest because it uses Google Autocomplete, but takes it one step further by generating up to 750 suggestions per keyword. But it autogenerates suggestions alphabetically for phrases that include words before and after your base term. There is no CAPTCHA or ads to distract advertisers from their in-depth researching, and the best part about this tool is how easy it is to navigate. If you want a simple and fast long-tail suggestion tool, I highly recommend this one.
It works with 129 Google domains, 83 languages, and is extremely user-friendly.