Equipment I can't live without.

Knives.... very important as you cut a lot of stuff in cooking.  You really only need 3 types for most applications. 
1) chef's knife  6-10" blade European or santoku style.  I like the santoku's my self but whatever you like.  I have three that I use and it's the workhorse knife of the kitchen.
2) paring knife 3-5 inch blade whatever you like.  It's what's needed for small items, sectioning citrus and the like.  Second most used in the kitchen.
3) serrated edge knife 8-12 inches.  Essential for cutting bread (duh) and excellent at tomatos.  Least used but not replaceable.

Not a knife but poultry shears are also VERY useful and not just for cutting open plastic bags.

Keep knives sharp.  I have a draw type sharpener as I find that the easiest to use but use what you are comfortable with.  Always remember that a dull knife is more dangerous than a sharp one.

Get the best quality knife you can afford (Amazon has good sales at most times) and take care of them.  Never toss them in the sink, cut on glass or porcelain or abuse them as you will use them every day and they need to be used safely at all times.

Other types of knives you can use as you see fit.  I personally don't need a boning knife or any of the others that are in the 20 piece sets (i do have an awesome cleaver but it's rarely used).

As a separate item if you can get a sushi knife get one.  These puppies are VERY sharp and are beveled to cut on one side only.  They are also very long as they are designed to cut delicate items in one long draw rather than by using a sawing motion.  Not often used but very handy and it makes a great carving knife.

Recipe of the post:
   Roast Beef Tenderloin
 Use a roasting pan with a rack for a good crust all around the roast.
Pre-heat the oven to 350 f.
Coat the tenderloin with a liberal amount of salt and pepper
Insert a digital meat thermometer (from 15-50 $ online and ESSENTIAL for cooking meat).
Cook to an internal temperature of 140-145 degrees remove from the oven and let rest for at least
15 minutes (the roast will continue to cook to a medium-medium well)  If you cut the roast before it is done resting it will be a bit underdone (nothing wrong with that) but all the juices will run out and it will end up dry.  I like to let it cool and then put it in the fridge for a while and cut very thinly for a very thin sandwich cut.  It will be the tenderest most flavor-full roast beef sandwich ever.  Cut moderately thin for a hot meal.  I know tenderloin can be expensive but at cost-co or sam's club it can actually be a relatively cheap cut when you buy it whole and vacuum packed.