Scenario: You press CTRL+K to focus on the address bar because you want to make a search (and not treat the input as a URL), but you don't want to use google, or whatever your default search engine is. So you press the down arrow key repeatedly to move through your list of alternatives until you reach your desired search engine. Here is a video demonstration of what I am talking about.
Improvement: After focusing the address bar with CTRL+K, instead of pressing an arrow key to go to the next search engine, why not just continue to hold down the CTRL key and keep pressing K? As it stands, inputting CTRL+K multiple times does not do anything beyond the initial input. So, it seems like there is prime real estate available in the competitive shortcut namespace just waiting to be used.
PS: I know this a supremely trivial matter—having to move your right hand from the K button down to the arrow keys hardly qualifies as an inconvenience—but I find myself in this scenario so often that any minor improvement would drastically improve my workflow.