Although it seems really random people having +forward on a mouse button isn't as weird as it sounds, as the default in Doom was RMB iirc. My housemate at uni used to use that setup.
Personally I use a fairly standard layout of TFGH (WASD transposed centrally to give access to more keys), although in single player games I usually can't be bothered changing it anymore and stick with WASD.
I still harbour fantasies of Microsoft creating some sort of centralised control mapping system and making support part of GFWL certification whereby you can map keys to common functions in one place and then games interpret those commands so it doesn't matter what keys you use, all the main functions like forward/back/left/right/shoot/reload/crouch/prone/zoom etc would be predefined to whatever you want and you'd only need to manually map a few bespoke keys for each individual game. Kinda like an integration layer approach.
As for the invert mouse thing, regardless of whether you love or hate it, one thing that is dead annoying is that it isn't always used consistently in game menus, sometimes you choose invert mouse but it was already inverted so all you do is change it back ASASERASDFAHJKJHAKSDAGGGGGHASDGDAHAAAAAAAAAAAARGH.