I haven't been to many. So many of my friends went to Storrs, Boston, or small private New England schools.
Happy Valley is pretty great.
Boulder is gorgeous but I visited in my mid 30s so I didn't exactly get the college/bar experience.
I was only ever there at night but Durham, NH (Univ of New Hampshire) seemed pretty cool.
UC-Santa Cruz has amazing views of the ocean but that weird run-down Cali vibe to it, at least the part I went to. It's probably the most unique campus I've been to.
Univ of South Carolina was underwhelming. Much of it looked like some industrial complex from the 1960s. No personality in the architecture. Some of the surrounding houses/neighborhoods are beautiful.
New Haven has its charm--I lived there for eight years--and Yale pretty much is New Haven so I'll include it.
I really wish I visited at least one big school in the deep south.