What are some examples of tier one/impressive extracurriculars for someone interested in science (biology)?

One of the most prestigious ecs you can have is competing in something like IBO (International Biology Olympiad) or in a national research competition (think Junior Science and Humanities Symposium, Regeneron Science Talent Search or etc). Competing at the state/national level for Science Olympiad in topics such as Designer Genes, Protein Modeling and etc can also look quite good on an applicant's profile. Basically, aim for national/international stuff since tier one shows you are the best at what you do and you proven it.