get a job
volunteer
get an internship
travel
AmeriCorps
job corps
national outdoor leadership school
a gap year sounds cool. wish I had taken one. instead, too much precious lil "parents" pressure to go directly to college. and not just any college, but it just "had" to be a certain one. and not just any major.
but whatever.
a gap year could be good, so you take a break from school. think about what you want to do after graduation. develop social interactions and job skills. life skills. unwind a bit.
although, esp for STEM majors, someone's academic skills might atrophy.
but, of course, atrophy how much and for how long.