[fenwick67]

Just a plain !w gives me English Wikipedia.

Usually if I need a certain engine I just guess the bang and it's usually supported and correct. !gm for google maps, !tineye for tineye, !wayback for the wayback machine...

[Freak_NL]

They are pretty predictable. I just tried !osm madagascar on a whim, and it opens OpenStreetMap, as expected.

Setting DuckDuckGo as the search engine for your browser's address bar means all these bangs work right there whenever you open a new tab.

[smnrchrds]

It depends on language settings. I have set DDG region to Canada and language to Canadian French. As a result, !w redirects mne to French Wikipedia.