They are generally all very good about need-based aid. Further details on merit:
WashU has at least a dozen merit full tuition scholarships per year. They especially like high MCATs.
Penn has I think ~20 full rides per year (21st century scholars program or something)
CCLCM I think gives everyone free tuition automatically
Mayo I think gives everyone like a 50% tuition scholarship automatically?
Northwestern gives a good number of merit full tuition scholly
Vandy gives ~75% of admits a merit offer for ~75% of tuition
UCLA does the Geffen program that gives not only full tuition, but also a living stipend
Michigan, Columbia, and UCSF I think have a handful of full tuition merit spots each year
U Chicago gives multiple $200k merit offers each year, again known for emphasis on high MCAT
Harvard, Hopkins, and Stanford have need-only policies and do not do any merit.