I don’t work in rails without the following:
coffeescript
haml
Zeus
guard
parallel-tests
But some of my favorite gems include:
Paperclip for image attachments and manioulation
s3_direct_upload for client to S3 direct uploads
cocoon for easy nested forms and associations
Font_awesome for scalable icons including spinners
newrelic for performance insights
Devise for user management
cancan for authorization
Here is one I just found that is amazing for events and recurring schedules: IceCube (for events) and recurring_select (for a nifty ui around IceCube rules)
I’m sure there are more but these are my favorites.
I’ve got to say that I’ve gone from really liking CoffeeScript to really much preferring JavaScript with ES6 syntax, especially when used with great libraries like lodash and ReactJs.
One I failed to mention but has been an absolutely amazing gem that has literally saved me hundreds of hours and thousands of dollars is Rubber https://github.com/rubber/rubber, for deploying and managing a cloud it is AMAZING.
If you combine rubber with a good unicorn/nginx front end, you get single command HITLESS deploys to your cloud. So nice!
On the front end side using guard-livereload is also invaluable. As you modify the asset pipeline seeing the visual results in real time without touching anything us great. Especially if you have dual or triple monitors
I found these gems to be very useful:
Paperclip (handling images)
Rack-cors (CORS)
Pundit (authorization)
Omniauth (light-weight authentication)
Active model Serializer (json objects to client)
Has_secure_tooken (tokenizer, pre-released for Rails 5)