I work in rentals on my mountain, and sometimes when its really busy you forget to ask if the person your helping is skiing or snowboarding and you get them the same type of boots the last person needed.
last year I got this Asian kid a pair of ski boots, he ask 'Dis boot I need' i say yes thats the boots you use on the mountain and go to help the next person, once it died down a little my boss sent me to a tec bench and the kid I helped had just gotten to the front of the lineup, when I walk by I hear the tec thats helping him all confused and I go up, the kid was pointing at the skis the tec brought and saying they skis? and making the motion of a snowboard, then saw a snowboard and said, I want that ski. so I took him back to boots and got in the right boots...
I think that was the funniest thing that happened in rentals, and we of course get a lot of people that don't know a thing about skiing or boarding.