Maria somethingorother.
When I was little and got in trouble with people who didn’t know me, I always blurted out that my name was Maria. Too much West Side Story at the time, I imagine.
Jane Air
Dori Fasolla
Lenore Poe
I’d give myself the same name as head honcho of the World’s Largest Platypus Importing Ring. Every time he got the whim to Google me, he’d get tied up in his own vanity and start reading stories about himself until the original goal was forgotten.
Or I’d use his Mom’s name. Who would want to shoot their mom? (recent events notwithstanding)
John Elway
It’s a chance to turn around my stinkin’ life.
Doing some genealogical research I found a remote cousin by the name of Bluebell Memorial Butcher. I wonder what her parents could have been thinking.
Jacob Eisner.
Because Jacob was my grandfather’s name, and I like both nicknames for it. Because Eisner is German for iron worker.
or
Hans Ingmar Muller. Because then my monogram would be HIM.
John Jacob Jingleheimerschmidt. 'Nuff said.
When I’ve needed an alias in the past, I’ve gone with Richard Hurt.
Smith P. McJones
Because I wouldn’t want to be completely ananymous, but not totally conspicuous.
The “P” stands for Pseudonym. I’m relying on my pursuers being very stupid.
Cecil Adams 
Jake and…? 
Jocko?
Ozamataz Buckshank
I’ve said it before, Mr. Underhill of course.
Jack?
Henry Hill. Just because you’re in Witness Protection doesn’t mean you can’t live a little dangerously.
Bud “Hieronymus” Incognito. But my friends will call me Jennifer. That’ll confuse everybody!
Hey! That’s my name too!
IRL or WPP?
I wouldn’t become involved in any court case that would result in me requiring witness protection. I wouldn’t want my life ruined just to put someone in jail. Plus, I put a lot of thought into my name, I’m not changing it again.