These are top and recommended testimonials extension for Magento 1 & 2.

1) Testimonials By Landofcoder
Impress your customers and enhance your store credibility by using our Magento 2 testimonials extension. Using this Magento testimonials module, you can monitor customer’s review and testimonial easily on a daily basis. Thanks to this you can convert more sale for your store.
Link: https://landofcoder.com/testimonial-extension-for-magento2.html

2) Testimonials By Magebuzz
The Free Testimonial Extension for Magento 2 allows the customers to leave their reviews about your products and services at ease. This will be a priceless source to gain trust from other buyers and motivate them to start purchasing in your store.
Link: https://www.magecloud.net/marketplace/extension/magebuzz-free-testimonial/


3) Testimonials By Elsnertechnologies
Happy Customers are key assets for online business. Let them to spread their view about your store. It will help to join new customers without any efforts.
This is an extension that will help to add text testimonial. Customer would be able add testimonial. Guest would be also able to add testimonial. every thing would be configurable from admin. Admin will allow customer and guest to add testimonial.
Link: https://codecanyon.net/item/magento-2-testimonial/18532977