There were most definitely plans for the Swiss, it was called Operation Tannenbaum, which was developed after the French surrender. But by then it didn't really have much priority since the country was fully enveloped anyway.

Also, the Swiss were everything but easy targets. With Hitler's breaking of the Treaty of Versailles in 1935, the military budget skyrocketed six-fold. On August 30, two days before the Invasion of Poland, the Swiss Bundesversammlung elected Henri Guisan to the post of general of the Swiss Army (something only happening in wartime, making him the most recent commander of the Armed Forces to date), who immediately mobilised the army on September 2^nd and sent an army corps each to the north, east and west with reserves in the centre and south (Operationsbefehl Nr. 1).

To quote Guisan from his report to the Bundesrat on September 7: "On Sunday, 3 September 1939, when at 12.10 Central European time, Great Britain declared war on Germany, our entire army had been in its operational positions for ten minutes."

Henri Guisan was very well aware of the strengths and weaknesses of the French Army, using the natural position of the country in the middle of the Alps to his advantage with his evolving Operationsplanung. He greatly improved a national defense concept that had been tinkered with since the 1880s and in 1940 finalised his Réduit National, a comparably easily-defensible Alpine core between the heavy fortresses of St. Maurice, St. Gotthard and Sargans into which the country would effectively move, slowing the attackers in the mountainous passes to allow time for a full retreat, ceding the Rhine lowlands to the Germans and destroying the transalpine routes behind them.

And they would most definitely have revolted against the Nazis, in late 1940 twenty-one people - among them two members of the national council, army officials and even the country's manager of General Motors - founded the Aktion Nationaler Widerstand, whose sole purpose was to fight and persuade the general population to fight the Nazi invaders. Their motto was „Als Schweizer leben oder nicht mehr leben.“ ("To live Swiss or not at all").

For further reading see also Jonathan Steinberg's Why Switzerland?

I'd like to offer a slightly different angle, which is that attacking Switzerland was not expedient for Hitler or the German high command. Hitler was not fond of Switzerland, and this could have lead to action during one of his unstable periods, but I think not otherwise.

Operation Tannenbaum (the invasion of Switzerland) planning was completed around October 1940. What was going on around then?:

• In July 1940, planing starts on operation Barbarossa, and they are presented to Hitler at the beginning of December.
• Berlin has just been heavily bombed in September for the first time.
• Germany moves more towards a strategy of invading for access to resources, and invades Hungary for oil.
• In November, the Italian debacle in Greece becomes plain.

By the time the planning is complete, Switzerland is just not a priority.

• It has few raw material resources.
• It is surrounded anyway, and is not a means to an end.
• Troops are needed for other fronts.
• It is not a threat. By this point, the German high command has a lot of balls in the air. It is deciding where to play whack-a-mole, as well as keep delivering victories for Hitler, no easy task*.

In addition to this, Switzerland was very well defended, and would definitely have fought.

'* As an aside, there is a view that Hitler was a decent commander to start, and got worse only as the war wore on. I don't agree with this, and think he was terrible the entire war. So there was a certain amount of luck he did not go off on a random anti-Swiss tangent.