Blender and OBS Studio are very good examples of FOSS software that are the best at what they do and can easily offer competition to even the commercial alternatives.
Most of all their design and UI language is consistent - something very rarely seen in FOSS software.
And they have incredible depth of features 90% of which are overkill for the casual user but the experts sure do appreciate them.
And the best part is the well-thought of extensibility and API story. Both of them have a very good community of plugins and extensions which add very useful features without feeling out of place.