# Tip
#tip is an extended command introduced in NetHack 3.6.0 that allows you to empty the contents of a container in your inventory.

Description
Using #tip and then selecting an appropriate container will deposit that container's contents onto the ground. Bear in mind that this acts exactly as if you had dropped all items in the selected container onto the floor - if you are levitating, any fragile objects you drop will shatter upon impact.
Tipping a bag of tricks or horn of plenty will use up all its charges in one turn, producing multiple monsters or comestibles as appropriate.[1] Tipping over an ice box will render all the corpses within unfit for sacrifice.
Tipping a container you own in a shop will automatically sell the contents to its shopkeeper.

The following information pertains to an upcoming version (3.7.0). If this version is now released, please verify that it is still accurate, then update the page to incorporate this information.

Tipping your worn helmet while next to a monster acts in a similar way to #chat, but may elicit different responses.
Strategy
Tipping is especially useful when you have no hands free, and you need to retrieve some curse removal item from your bag. It will also allow you to drop a stashed scroll of scare monster from its bag with a single action.
If you are in a hurry and/or using a (preferably spare) container, tipping can be used to sell off junk and other items quickly in shops, or else mass-identify their beatitudes on an altar.

References

↑ pickup.c in NetHack 3.6.1, line 3058