webpack in all its complexity.....ya baby (austin powers voice)

For the moment the tool i choose is Grunt, it's similar to Gulp and Brunch, but i think that have the more wide plugins repository.

npm itself ofc, I also have been using gulp, bower and other tools. You really don't need that extra layer around a layer already. Good packages provide good JS API so there no need of lot of code, sometimes my npm scripts are even shorter then gulpfile.

For 2016 you have to use rollup, I don't recommend anything else and especially huge webpack where you need months to understand it, days to set up. Rollup just install and use out of the box. I have found many problems using rollup with gulp, and finally you always have npm packages with latest version and you can use directly their APIs and not waiting when gulp-x plugin will be released.