Okay. There is really one that stands out way above the rest. My garden knife. It is the best thing I ever bought. It is from Fiskars, the company know for making scissors. This thing is AWESOME!
You can see by how dirty it is that I use it a lot. It has a plain blade on one side, a serrated edge on the other. Not terribly sharp or I would have lost a finger by now. The point is perfect for digging weeds and the width makes it more efficient in the task. The shape means I can use it as a trowel. The edges help cutting through turf or other roots. Just the best thing ever.
Other items that I couldn't do without are the flat-pronged pitchfork for turning compost, really good clippers in two sizes for large and small tree shoots and branches, a hand cultivator for breaking up soil, and a broom and a hand brush for sweeping up the patio and sidewalk.
Buckets are always a great thing to have around. I eventually plan to kick one, but not for a few decades. They can be great for storing things -- like the cat.
Yeah, I've used this photo before, but I love it so much that I have to put it out there again. Naomi is also a great garden tool since she is a hunter and will chase birds, mice and insects that might damage my fruit and veggies. Not so much with the squirrels since she has made friends with them, but they are still cautious. She is a predator, after all.
The most heavily used tools in the garden, by far, are my brain, my hands and my back. And, of course, my butt. I would be nowhere without the back of my front.