What give should I give to a guy to show my appreciation?

He's my partner at work- I worked under his guidance. I want to give him some token of appreciation to show how much I appreciate his guidance, for teaching me valuable things and for being such a good friend who takes good care of me. My contract is almost ending and I want to give something before I leave. I want to give something that would last for a longer time.

What give should I give to a guy to show my appreciation?
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