Toki Pona
Toki Pona is the world's smallest language. With barely over 100 words, command of the language demands simplicity of thought and explanation. For Sonja Lang, Toki Pona's creator, the limited vocabulary was designed to change how people think, turning descriptions of everyday concepts into creative challenges. There are no prescribed conventions or cultural norms.
As a result, things are described differently by different speakers and sentences are often ambiguous and highly context dependent. So, to make sure that your intended meaning is conveyed properly, you need to be hyper-aware of the perspective of your audience. While this is disadvantageous for things like legal documents, Toki Pona is easy to learn quickly, making it ideal for communication between people who currently don't speak any languages in common.
If you're interested in learning more about Toki Pona, check out this interactive tutorial.