One day, one of my friends asked what tools/gems I normally use for Rails. My answer to his question was trying not to use many gems ;-)
As a software engineer, I most likely use only tools and libraries that came with the development tools and languages. To me, having or using many third party vendor's libraries keeps me very unorganized when developing. I know I have to admit that I am little lazy and reluctant to take new comers. But so far, it has been working perfectly for all of my projects. The projects were neat and other members in my team were able to easily compile/maintain my original projects and source files as well.
Going back to the original question above, these days I use the following plug-ins and gems only for my Rails projects and try not to use any other gems in a project for the same reason. The following gems and plug-ins have been pretty much enough for my needs, but again you would need more than these for your own projects. So, please ENJOY with Rails freely!
Faker & Populator
** I really thank the developers, who built those and make our jobs easier **
What gems and plug-ins are you using with Rails for your project?
By the way, I made one-page Rails' cheat sheet for my friends and hope that this would be helpful to any Rails new developers.