Answer:
If you have me, you want to tell me. If you tell me, you don't have me.
Other terms for this handy device include doohicky, doo-dad, and whatchyamacallit.
Without coolant, you'll have some trouble with this.
Which word contains all 26 letters?
It has the biggest wall and is also used when drinking tea.
My days are numbered. What am I?