…all the primary care blockbusters from the last few decades - statins, antihypertensives of various types, antihistamines, acid blockers, SSRIs, etc.
An effective SSRI (or SNRI or dual-acting agent) without the typical side effects could be a very big-selling drug, IMO, despite the wide array of generic agents. However, inasmuch as the most prevalent side effects of these drugs are mechanistic, such a product may be almost impossible to come by.