I have put together a list of the 5 most important tools one can have as a DIYer. Not only have these tools allowed me to accomplish most of the things my wife asks me to do but they cost very little money. Plus they pay for themselves with the time and energy saved.
#1 Cordless drill
If you do not own a cordless drill by now then do your self a favor and when you are finished reading this, GO PURCHASE ONE! I think I use mine every other day.
#2 A Decent Hammer
Trust me there is such a thing as a bad hammer. You won't know it until you pick up a GREAT hammer.
Whether you need to cut PVC, galvanized pipe, copper, a stripped screw, anything, a hacksaw can get the job done. You can even use it to cut very small pieces of wood although I would not use it for wood that is very thick as you will be there for a long time. You can purchase one under $10 and replacement blades are much cheaper.
#4 Electric sander
At just under $30, this little guy will save your wrists from aching after sanding your dresser before refinishing it.
#5 A good Multi-tool
Just like Les Stroud, I never leave home without it!
A close runner up would have to be my laser level. This tool has helped keep many of our pictures in line and level on the wall as well as make sure shelves and tables that we build are level.
Did I miss anything? Do you have a different list of essential tools?