Felt-tips dry out if you don't put the lid back on.
I had a big pack of felt-tip pens in different colours.
She carefully coloured in the sky with a blue felt pen.
Some of the items were circled in red felt-tip.
She had written her name inside the book in felt pen.
I had felt-tip pen all over my hands.
The pattern on the cup looks like it's been drawn on with felt-tip.