ALL of them. Sitting gaskets like transmission seals and crank shaft seals the oil will eventual drain away and evaporate. When you take off the either burn up from being dry or tear. Also any bare metal inside the engine will eventually start rusting. Driving the car regularly takes care of it. Gasoline will also go stale and cause issues that can get expensive. You need to run about half a tank of fuel through a car about once a month and fill back up to keep the fuel fresh. You don't want to leave the tank empty unless you have to put the car into long term storage and if you need to put it in long term storage you want to do it somewhere somewhat temperature controlled. If the vehicle is in service you want to leave the tank full so as to have a minimal amount of air in the tank. The more air in the tank the more condensation that can form and settle to the bottom of the tank. That will accelerate how fast the fuel gets stale, cause rust (if the tank is metal) and if enough collects it can get sucked up and clog the fuel filters, injectors and damage the fuel pump. This s VERY big problem with Ethanol fuels. Ethanol fuels can hold a lot of water and burn it safely but they have a point where they go critical mass and the water will drop out of the fuel. You hit that point you go from the fuel having 1-2% water suspended in it to having a 1/2inch of water in the bottom of the tank overnight.

You want to get it on the hwy for 15-20 minutes a month and get it fully up to temperature so that it gets hot enough to evaporate any moisture that may have formed in the engine and collected in the oil. If you use it very infrequently then throw a cooler in the trunk and do your groceriy shopping the next town over to get the car some exercise.