On Firefox I have
g - google
ddg - duckduckgo
yt - youtube
w - wikipedia
etc.
easy to type without the bang at the front (Google and Wikipedia are defaults, not sure what the other ones are). I gather on DDG you can use them at the end so you need the ! as a delimiter.
Also Stackoverflow's search and many other site searches are totally rubbish. Not a bit, but totally rubbish. Here's an example:
"!so c# read file" => this delivers useless results, the top result being "Reading Excel files from C#"
Compare that to "stackoverflow c# read file" on google, which delivers what you actually want, with the question "Reading From a Text File in C#".
What? It redirects your browser to Google, it's you doing the search, not any other entity. They don't proxy or anything.
I couldn't correct it because of HN's stupid 5-comment policy that applies to comments made in all threads combined, and couldn't edit the original comment with a correction as it had been more than an hour. :/
Setting DuckDuckGo as my default and using !s means I can search any of those sites without having to go to them first.
It takes a step out of the process.
A few of the ones I abuse constantly:
!g - google
!bi - bing image
!yt - youtube
!so - stackoverflow
!w - wikipedia
!py - python docs
The exhaustive list is here: https://duckduckgo.com/bang.html