I'd say quite a lot of GoDaddy services require a domain to be registered. But that does not mean they need to be registered with GoDaddy.

Services that do need a domain registered with GoDaddy:

    Domain Name Registration
    Transfer Domain
    Bulk Domain Name Registration
    Bulk Domain Transfers
    Internationalized Domain Names (IDN)
    Discount Domain Club
    Domain Buy Service
    Go Daddy Auctions®
    Private Registration
    Business Registration
    Deluxe Registration
    Protected Registration
    Certified Domain
    Premium Listing
    Premium DNS
    Domain Backordering
    Domain Management

Services that don't need a domain registered with GoDaddy:

    CashParking®
    Web Hosting
    WordPress Blog Hosting
    Virtual Dedicated Servers
    Dedicated Servers
    Managed Hosting
    Virtual DataCenter
    Dedicated IP
    Go Daddy Hosting Connection®
    Website Analytics
    Search Engine Visibility
    Website Protection Site Scanner
    Hosting Management
    Go Daddy Email
    Hosted Exchange
    Online Calendar
    Fax thru Email
    Online File Storage
    Email Marketing
    Email Management
    Webmail
    Search Engine Visibility
    Website Analytics
    Email Marketing
    Business Consulting
    Business Solutions
    Quick Shopping Cart®
    Merchant Accounts
    SSL Certificates
    Code Signing Certificate
    Website Protection Site Scanner
    SSL Certificate Management
    Turnkey Reseller Plans
    API Reseller