TabNine is the all-language autocompleter. It uses machine learning to provide responsive, reliable, and relevant suggestions. It also works in tandem with existing text suggestion to give better experience. Check it out at https://tabnine.com/.
Cssstats is an intereseting and a useful tool that helps graphic designers and front-end developers to access detailed statistics on all CSS files of any project. You can access it at https://cssstats.com/ or clone it locally from https://github.com/cssstats/cssstats.
Logstalgia is an intuitive visualization of Apache/Nginx format server access logs. Basically its a pong game where successful requests are hit back by the paddle and unsuccessful go missed. Developers can visualize live server logs or pre-recorded ones. To find out more visit https://logstalgia.io/.
This is an amazing tool created by Pavel Dobryakov based on WebGL. It uses fluid mechanics equations for life like fluid simulations and in addition to that it has a great looking visual interface. You can give it a try at https://paveldogreat.github.io/WebGL-Fluid-Simulation/ and checkout the source code on github.