Winter bike/Commuter/Tourer. Alloy, mudguards, rack, cheap(er) components that can be replaced when the salt eats them.
Summer/Best Bike. Carbon, skinny tyres, no rack, no guards, higher spec stuff. Light, fast, fun.
Hardtail MTB. Off road hooliganism, trail centres, round the park with the kids.
Fixed/Pub bike. Old steel frame. simple, easy to maintain, absolute bas**rd on the hills round here.
That just leaves for N+1:
Full Sus MTB - If I ever get brave/stupid enough to want to throw myself down a mountain in body armour.
Recumbent - Just cos they're different.
Folder... Hmmmm struggling for a reason here, give me a bit I'm sure one will occur to me eventually.
My Problem is Mrs Kes and the Kids are on the same page.... need a bigger shed (and a better paid job).