Over the years, I've bought so many knitting tools, and these are the ones I reach for over and over and over again.
There are some really obvious ones I won't include in this list -- anything that's so essential to the craft it couldn't be done without it, like knitting needles and some kind of string. Beyond that, I'd say well-designed and dependable knitting tools are maybe not essential, but so nice to have. I do get really rapturous when I talk about good tools; do you?
1. Stitch markers
There are so many kinds of stitch markers, and everyone has their favourites. I've tried all different ones: dangly, metal, plastic, homemade, you name it. Lately the ones I love best are plastic rings, because they're smooth, don't snag, are cheap, and come in a million colours, and dangly snag-free ones made from beading supplies.
I usually use one dangly one to denote the beginning of a round, if I'm knitting circularly, and use smooth plastic or metal rings to mark places where shaping will occur.
I also occasionally use locking stitch markers too, and the single way I use them most is to mark off divisions along an edge where I need to pick up stitches. Say, for example, I need to pick up and knit 80 stitches for a collar. I'll use the locking stitch markers to divide the neck opening into eight sections, and then I know I only have to pick up and knit 10 stitches in each section. I usually end up with a really nice pick-up edge, with the stitches evenly divided, and the correct ratio of pickup stitches. As well, I never have to redo the pick-up, because I can correct any spacing mistakes as I go and not have them all pile up at the end.
2. Clover bent tapestry needles
I've got so many tapestry needles, but this is the one I always reach for. It's not sharp, so it's perfect for hiding ends without piercing the work (if that's what you want to do), duplicate stitching, and grafting. Not only it is blunt, but it's somehow exactly the right bluntness so that you can get it wherever you need it, and it doesn't go where you don't want it to. The eyes are huge and easy to thread; the shaft is smooth and never catches your work; the bent tip is excellent for lifting and poking exactly where you want. They come in a set of two (though I hope you never lose one) in their own perfect carrying case. Best ever!
3. Clover locking row counter
Again, I've got tons of row counters, because I always have so many projects going at once and use a counter with nearly every project. However, this is my all-time favourite ones: they lock so you don't get any accidental clicks when you carry the project around (or when your three-year-old decides to get click-happy with your counter), they're durable, and they click very satisfyingly. I don't use this, but they do also have a place to attach a string, should you want to keep yours around your neck.
That's my first three; I'll tell you all about the last two on my list on Wednesday. See you then :)