Tea tree oil - I use this for so many things.  Any kind of rash, feminine problem, infection, skin problem, etc. can be treated with tea tree oil.  It both cleans and heals at the same time, and is effective against bacteria, fungus and other nasties.  And it feels very soothing and cooling.  Diluting it works best but I've used drops of it straight as well.  This has also worked on gingivitis and other gum problems.

Apple cider vinegar - I use this for cleaning my house sometimes, but most often this is used in conjunction with the tea tree oil in cleansers and toners for any problem related to the skin.  It is also good to gargle for a sore throat - any kind of disinfecting of the body.  I haven't taken it internally but there are a plethora of things that it can do as it is considered a detoxifier.

Chili powder - This is by far the best virus prevention I have used.  For a very strong dose, especially for a sore throat, put at least a teaspoon in a tall glass of orange juice and chug it.  The chili will cleanse your throat and fortify your immune system (along with the vitamin C).  For a less difficult way, make some fresh, really spicy salsa and eat at least 3 times a day.  

Baking soda - Besides cleaning the house with it, this is also a great remedy for sore throats, just dilute at least a tablespoon in a small cup of hot water and gargle it.  I have used it for an ear ache on myself as well, using the same mixture and just sitting with it in my ear for 10 minutes at time.

Rosemary - Rosemary has some great external uses, but we have mainly used this for circulatory problems.  A strong rosemary tea (even from the dried rosemary you would have in the kitchen) can cure headaches, and also can keep your menstrual cycle running on time.  I have found it to be very gentle so several cups works better.

White and green teas - This is a no brainer, but I consider it part of our health kit.  Besides boosting our immune systems this helps us feel a little less fatigued and helps us slow down and de-stress at the same time.  The process of drinking tea is therapeutic in itself. :)