I'm wondering what is the best mouth rinse that fights gingivitis?

Several choices: Commercial mouthwashes as crest and listerine work well but the best is chlorhexadine but that is by prescription. Use an alcohol free mouthwash you are best off with toothpaste, floss and a soft toothbrush see a periodontist to help you keep your gums healthy.

None!: Gingivitis is from gums not being cleaned well with brushing and flossing. Mouthwash will do very little.

With brush/floss: Along with flossing good then brushing, the use of any chlorhexedien containing mouth rinse would help fight against gingivitis causing bacteria..

Ask your dentist: When you see your dentist, ask which applies to you! Certain medical conditions or medicines, cause dry mouth and that would require a specific type of mouthwash. Other medical conditions, have specific requirements in a mouthwash and might even require a prescription mouthwash. So find out what's best for you and follow the professional advise!

Sealed by ADA: The mouthwash alone will not solve the gum inflammation. The American Dental Association recommends antimicrobial mouthwash to help prevent and reduce gingivitis. Any mouthwash recognized by ADA and approved by FDA will help. Healthy habits and good oral hygiene is the key for a gum inflammation prevention.