The short answer about Switzerland was that they'd prepared extensively against an invasion, both on an organized level where the army was fortifying a "National Redoubt" in the mountains and promising never to surrender; and on an individual level where rifle-shooting had been the national sport of Switzerland for years. All these preparations - combined with a threat to blow up every rail and road tunnel through the mountains, which were vital for German-Italian civilian trade - made an invasion just costly enough that Germany never thought it would be quite worth it.

For more details, you might be interested in these two previous threads on the topic, or read Dr. Stephen P. Halbrook's Target Switzerland for more information on Swiss defensive preparations and determination.

hi! you may be interested in this section of the FAQ (link on sidebar):

Neutral countries during WWII