Its very hard to fly into Liechtenstein And most European countries in general, I've visited by land/rail.

But also, I have driven overland from Rio to Lima, as well as Nairobi to Cape Town - so anything in between will not have flown into on FM.

I am also counting these as 'countries' on my list (although I am sure some will disagree): If it checks/stamps a passport, it goes on the list I say.

Taiwan
Palestine
Cook Islands
Hong Kong
Macao
New Caledonia
Guam
Gibraltar
North Cyprus