Marissa - mah-rissa
Marisa - mah-ree-sa
Portugal
I don't know any Marissas, but I do know some Marisas (all of them pronounce their name mah-ree-za). It was fairly common about 10-15 years ago, and is still used (usually by young people with lower income and education level - name trends, please don't sue me for this); also common in the Gipsy community. Generally it's considered as a 90's trendy name.