First and four most are the ones that grow off the ends of my wrists. Seriously; fingers and hands are my favorite kitchen tools.
After that, it should go without saying, my knives.
I never gave this much thought, cuz I use all my tools and utensils about equally. So I take the approach, if I had to give one up, which would I most miss. Looking at it that way, I offer tongs as a hesitant third place.
i don't think that knives(sharp) even need to be mentioned, for obvious reasons...do like ky's hand and fingers answer...cool......two things i use everytime i cook or do anything in the kitchen every single day, are tongs and rubber spats...love them both equally... wish there was a better potholder for the oven...something not so bulky, definately not silicone or those awful mitt thingys... while bar rags are okay for stove top pots, they are a little thin for commercial oven use i use thick washcloths for that...
Can't live without 'em. But who could? /img/vbsmilies/smilies/crazy.gif
Seriously though, even though there's nothing "pro" about Westmark's slotted spatula/tongs, and while I could live without them, I love them.
In case it's not obvious, the tongs come apart and become two... wait for it... spatulas. Working two together gives you a lot of surface which can be helpful with big pieces. The spatulas themselves are slightly curved, and when they're put together as tongs, they can be oriented to squeeze or cup. Where they really shine is as fish and schnitzel tongs...so gentle.