There are lots of apps available but it is often difficult to screen those that might be useful in your class. Emerging Education Technologies has published a list they feel are useful for teaching critical thinking skills. Check out the complete article at the source link below.

The most important gift that educators can give to students is the ability to think critically. Critical thinking is the ability to take information, then instead of simply memorizing it…

Source: 10 Fun Web Apps, Games, for Teaching Critical Thinking Skills — Emerging Education Technologies