What have you found to be the best online survey, feedback, and customer discovery tool?

Largely considered valuable given their popularity, here are a few of the most recommended survey tools :

• Easy to use, for first time survey builders: SurveyPlanet
• Beautiful and intuitive survey forms: Typeform
• Great for smartphones while being more advanced but still straightforward: SurveyMonkey
• Survey offline; or rather, create the survey for offline: QuickTap
• One click feedback, great for Net Promoter Score: YesInsights
• Gamified surveys: Survey Anyplace
• On Facebook?  Here’s a chatbot that surveys: Surveybot

Would love to hear about your best practices, other recommendations, or tips.  Any other survey approaches or tools you use?