Get approximate IP details.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Get all possible details about an SSL certificate.
Get all possible details about a domain name.
Ping a website, server or port..
Compress and optimize images for a smaller image size but still high quality.
Make sure your passwords are good enough.
Extract email addresses from any kind of text content.
Take an IP and try to look for the domain/host associated with it.