That may sound pretty basic, but I've been in many a kitchen where people didn't realize what difference that One Good Knife makes. Heck, I didn't realize for the longest time. Until someone hands you a good quality knife, its very hard to imagine just how awesome cutting up a piece of cucumber can really be.
There are a million websites and articles that deal with the subject of choosing that One Good Knife, but most agree that an 8-10 inch Chef's Knife is the one to get. There are a lot of options to choose from. Stamped or forged? Carbon steel or stainless steel? Full tang or partial? Most of this is going to be up to you.
My first "good" knife was a stainless steel Farberware santoku I bought for $10 on a whim at the grocery store. The difference between that and the knives from my $20 knife set from college was night and day. Suddenly, finely chopping parsley was no longer an exercise in futility.
Now I have an amazing steel set my Dad made for me (I am one lucky cook!) that contains everything under the sun. I have to take much greater care of the blades to prevent rusting, but boy-oh-boy is it worth it. Personally, I prefer the steel knives to the stainless steel since they really hold a much better edge and tend to be tougher all around (I am not a gentle kitchen flower).
This is a good place to start for knife knowledge, but spend some time searching and reading before you make a choice. If its at all possible, set yourself a budget, and trek out to a store that sells kitchen supplies (a restaurant supply store would be ideal). Get your hands on the knives, quiz the sales people, and try to pick something that feels right. You don't have to spend a fortune, but even a $30 knife can feel like an beautiful extravagance if you've been struggling with terrible equipment.
You should definitely pick yourself up a honing/sharpening rod. I'll talk about those next week, but if you're going to shell out some cash on a good knife, you'll want to take care of it.
