Experience-based and intuition-based testing techniques, such as error guessing and exploratory testing, can be valuable in uncovering defects that formal techniques might miss. These approaches leverage the tester's knowledge, intuition, and experience, providing a complementary layer to more structured and formal testing techniques.
Reference: ISTQB CTFL Syllabus, version 4.0, discusses the role and benefits of experience-based testing techniques in supplementing formal techniques.