TamperMonkey is a pretty handy browser extension that makes it easy to quickly write up some functionality to add or alter the functionality of a web page. Effectively, you can write a simple browser extension known as a "userscript". Here are the userscripts I use, including the ones I've written myself.
DuckDuckGo: Google Jump by modula t.
Quickly jump from DuckDuckGo search results to a Google search for the same query with
EmuParadise download script by Eptun
Restores the rom download links on emuparadise.me.
Wikipedia: Use Desktop Site by modula t.
Automatically redirect to the desktop version of Wikipedia (in case you get a link to the mobile version).