How many Columbo guest stars had their own TV Show
Here's a few
Gene Barry - Bat Masterton,Burke's Law,The Name of the Game
Jackie Cooper - Hennessy
Martin Milner - Route 66,Adam 12

In some of these, it wasn't just "their" show, but they were fixtures of a series. The following murderers each were in a regular series:
Stitch in Crime
Lady in Waiting
Death Lends a Hand
Fade into Murder
Old Fashioned Murder
Case of Immunity
Matter of Honor
Exercise in Fatality
Candidate for Crime
Negative Reaction
Deadly State of Mind

Also, the victim in Lady in Waiting and Lovely but Lethal.

Sorry, I didn't put the names/shows, but I'm sure they will all be familiar when you think about each. Surprising how many there are, and I'm sure I've missed some...

IDENTITY CRISIS and BY DAWN'S EARLY LIGHT
TROUBLED WATERS
DEAD WEGHT
RANSOM FOR A DEAD MAN (The only Lee Grant show I can name offhand is a pretty short-lived one called "Faye," but there might be others.)