Objektiv

Brilliant! Still works under 10.13 and does exactly what I need it to - and it's free! Definitely worth trying in later Mac OSs (so long as the default browser can be set using the General System Preferences pane). Note: when you first open Objektiv it needs to be set as the default browser (there's an automatic System prompt to allow this). You can then use it to switch default browsers easily from the menu bar. In operational principle, it's similar to LinCaster, but it serves a different purpose and offers different functionality so the two complement each other. Indeed, it's a great way to switch between normal browsing and browsing via LinCaster (which lets you set the default browser on a per-link basis).

In Yosemite it now cannot seem to work, instead a Notification is triggered, and when clicked the General System Preferences is opened and there you can make your choice..

Great little app (I'm on 10.8.2). You can switch your default browser either using the menu bar icon (which conveniently displays the icon of your current browser), or by setting a global hotkey via the app's preferences. When you press that hotkey, an overlay window pops up, displaying icons of all your browsers - to make the overlay window disappear, you need to either select one of the browsers or click outside the window. There's also a thoughtful option to hide browsers identified incorrectly by the app (click the menu bar icon to display the browsers, then press ALT. Minus signs will appear beside the browsers; click the one you want to hide). Suggestion: it would be nice if the same global hotkey used to display the overlay window, could also be used to make that window disappear.