I use alternate bangs all the time, which is a major win for DDG, as it skips the "go to the site first, or specify "site:<host> <search>", which actually is NOT equivalent as bang searches use the site or service's native search.

Fave bangs:

!w wikipedia

!wikisource WikiSource

!etym Online etymological dictionary

!ngram Google Ngram viewer

!trends Google Trends

!gbooks Google Books

!scholar Google Scholar

!tineye Image match search

!so stack overflow

!hn Hacker News

!twitter Obv.

!thread Threadreader App, Twitter thread presentation, preferred to above ;-)

!img Image search (now DDG, Google Image is !gimg)

!worldcat Worldcat union catalog

!osm Open Streetmap

!wayback Internet Archive Wayback Machine

!archive Internet Archive global (non-Web + web) search

!dict & !define Word look-ups

!s startpage (proxied Google search)

!bangs will give you a list of bangs / search form for patterns.