I likely have too many. But I couldn't live w/o a couple of good sturdy trowels (and even then, I sometimes manage to break them), a couple of good dandelion diggers. I like to keep one of each hanging in the garage - accessible at the front of the yard - as well as in my tool shed in the back yard. My garden diggers are a sturdy spade - not too large - and a good fork. I need and have just one of each. The old spade got moved to the garage for lifting ice from the driveway in winter.

But I have a couple of Lee Valley tools that I couldn't live without.

One is the Loop Hoe - http://www.leevalley.com/US/ga...
A wonderful tool to fit between plants in a crowded city garden.

The other is the All-Purpose Lifetime Weeder - http://www.leevalley.com/US/ga...
This is VERY sturdy and will do just about everything.

Oh and my favourite Felco pruner - http://www.leevalley.com/US/ga... I think mine might be #6 - it's not too large, but it's a work horse.