decoy callsign is common. Other interesting ones that have been used in the past include: fear, anon, order, rudy.

I hate when I watch a southbound flight bypasses Cuba and NAS Camp Justice!

Yes. Depending on the mission, military aircraft use either their standard Squadron / Wing callsigns with tail#, or a randomly assigned callsign from an ATO (Air Tasking Order) if conducting combat coded missions. Most callsigns are 4-6 characters in length, and designed to be easily understood. Also, the ATO is designed such that no two callsigns would sound similar with each other so they won't be misconstrued in a reduced comm / jamming situation.