Just college teams?
I was thinking about the pros:
NBA has the Utah Jazz, Orlando Magic, Miami Heat, and Oklahoma City Thunder.
NHL has the Colorado Avalanche, Tampa Bay Lightning, and Minnesota Wild.
NFL teams are all plural.
MLB is kinda "iffy", namely the Boston Red Sox and the Chicago White Sox.
MLS is chock-full of singular names. It's easier to list the teams that have plural names out of the 19 existing franchises: New York Red Bulls (ex-New York-New Jersey Metrostars), Colorado Rapids, Portland Timbers, San Jose Earthquakes FC, and Vancouver Whitecaps FC. The last three were christened after old NASL teams of the '70s, with the "FC" suffix added to a couple of them.