The layout I work on with my daughter is British prototype "OO" scale (1:76) equipment. I've always been kind of an Anglophile, and it just appeals to me. I even have one of Hornby's live steam Mallards in OO. That's a pretty cool piece of engineering. (My unboxing video here if you're interested, and a rather wobbly one of it running here.)
I also have several pieces of British N, though no layout to go with it. Someday I will build a small shelf layout with it.
I've seen some really beautiful British O (including these amazing Mallards) but they are too rich for my blood. I've been tempted to build a couple of the wagon kits from Parkside Dundas, as they are reasonably priced, but then I'd have nothing to pull them. Maybe sometime.
Fred