There are not many things two people can use at the same time. Though, there are some, for instance, tea bags for two:

..which come in a tea cup for two.

From MeetSebastian.com

Or another version of a cup for two by Tonerico Inc.

There are also Smittens for two by designer Wendy Feller. The mittens are handmade in Seattle.

Yours for $34.00

Then there is Tandem umbrella, also for being inseparable. Produced with Jasmine Raznahan.

Tandem Umbrella