AWS Secrets Manager
AWS Systems Manager Parameter Store
AWS KMS
Google Cloud KMS - Cloud Key Management System
Azure Key Vault
confidant - https://lyft.github.io/confidant
keywhiz - https://github.com/square/keywhiz
knox - https://github.com/pinterest/knox
strongboxsafe - https://strongboxsafe.com
conjur - https://www.conjur.org
+ many more
Ansible Vault - probably not competing directly
I am pretty sure companies like netflix, facebook, uber, tesla and others are probably using their own in house creations.