It really depends on the person and how well you know them and how long they have been with the company. Our manager retired a few months ago. He had been with the company in the same area for most of his career. We buy nuclear fuel so what we did for him was to contact all the people we knew in the industry and got golf balls (he is an avid golfer) from every company and got him a nice display case to put them in. Most people sent 3 packs or more of the golf balls so he also ended up with a nice bunch to practice with. We also got him a putter.

If you know him well enough, there may be some hobby item that would be good to buy or a gift card to a place they would enjoy shopping.

I'm personally not a big fan of a gag type gift that will be laughed at once then either collect dust or be thrown away.