Judge.me Product Reviews App

I think this is one of the best apps on Shopify. Not nearly enough companies know about it. For absolutely no money they offer a really great, reliable and reasonable service. There's no bells or whistles, but it does the job and gets reviews. If you do want bells and whistles however, it's just a fraction of what other similar apps charge, and it's just as good.
Would highly recommend - I've used Judge.Me for years (both the free and paid for versions).