Number came up on caller id - where the name should be was also the number, only without the dashes.
Picked up and immediately disconnected - that way, they don't get to wait and hang up on my answering machine.

Showed up on caller Id on my mobile.  I just ignored it.

Called me this morning on cell, never answered. It never left a voicemail.

This is a new one. It just popped up. Kinda like wack-a-mole, I put one annoying telemarketer (or whatever) into my call blocker (for Android, I use Call Control, its excellent) and another one shows up. OK, done. Won't bother me again.

showed up this morning, ignored