Hero Picker

Another team composition tool that can help you figure out which heroes work best on which maps. This one is interesting as it provides a "default preset" for common team compositions such as "Deathball" and "Dive" -- even relatively new but highly popular compositions such as "GOATS" are included.

Overwatch Team Generator

This interesting tool allows you to build different team compositions based on the enemy team compsition, map, different metas, and similar. There are a lot of options, and it's quite useful for quickly sorting out team compositions and the best hero you can currently pick for your team.