nw.js of https://www.messenger.com/ because I'm lazy.
I built nw.js loading up messenger.com, simple.
Open messenger.exe
Login like you would normal do at https://www.messenger.com/
Enjoy not having to open a browser, nativate to https://www.messenger.com/ and login.
Currently only built for windows, but it's made with nw.js so you can no doubt build it for OSX or linux