Car Filters and Wipers

Air Filter - check your air filter each time you get your oil changed. The air filter is designed to keep dust, leaves, etc... out of your engine as it draws in air to be mixed with the gas and spark from your spark plug. If the filter is very dirty it can keep the right amount of air from getting through thus your mileage will suffer and the car may not run as well.
Gas Filter - a gas filter keeps contaminents from entering into your engine and it's role is an important one as well. Check your manual to see if and when this should be replaced. Many gas filters will not allow you to easily check them and may even need to be replaced by a mechanic.
Wipers - when it comes to safety equiptment in your car the windshield/wiper system and the brake system are probably the most important. Check your wipers each month to make sure that the rubber is pliable and doesn't have cracks or rips. Be sure to replace them with a new set as soon as wear is showing as they are so vital to you seeing in inclimate weather.