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

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..which come in a tea cup for two.

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From MeetSebastian.com

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

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There are also Smittens for two by designer Wendy Feller. The mittens are handmade in Seattle.
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Yours for $34.00

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