We track feature usage. And as it turns out, along with the "core" helpdesk functions, like tight email integration (creates tickets from incoming emails), or "single sign-on" (authenticates users against the company's existing accounts), here's some lesser known but VERY productive help desk features our customers love:
Our helpdesk app, both the SaaS and the self-hosted version - is powered by SQL Server. The SaaS version additionally uses S3 (to store file-attachments), Redis (to persist in-memory cache between deploys and restarts) and other fancy cloud stuff, but there's still one big ass SQL Server database at the heart of it.
And this Christmas we've migrated it to Linux.