Dang, you beat me to it! That was the FIRST thing I thought of when opening this thread. I mean, a little boredom’s a small price to pay for unlimited power…
Runners-up:
One of Comte St.-Germain’s mortal girlfriends 
Nita Callahan from Diane Duane’s wizard series (actually, just myself as a wizard in that world would be great)
The X-Men mutant chick who can shift shape, only I wouldn’t be evil.
Dad?
what? no one wants to be Indiana Jones?? i would proudly be him
I’ll second Patsy Stone from Ab Fab and Elizabeth Bennett.
I wouldn’t mind being Alexis Morel-Carrington-Colby-Dexter for a while as well though not permanently - I’m not that mean 
[hijack] (Sorry!)
Whereas I, FP, had already speculated on the possibility that your handle might mean you’d share my devotion to Sayers. 
[/hijack]
Time to break out the new sig.
I’m supprised at all the votes for God. He/She/It must havee one of the worst jobs possible. Omniscience and omnipresence just suck, imagine knowing every bowel movement of every animal in the universe, nit just knowing but being there as well! ( OK so lieu might still be up for the job )
Nancy Drew.
Except it would now be “The Later Years.” Twenty-six year old Nancy has kicked Ned to the curb (it turned out he was only using Nancy for a beard, which explains why he never tried to make a move). Daddy Carson Drew, famous attorney, has retired and Nancy has shuffled him off to the nursing home and gotten power of attorney over his large fortune. She has replaced the doddering, lazy, bigoted old housekeeper, Hannah Gruen, with a really hot butler named Raoul.
I would tool around in my blue Jaguar XKE convertible, solving mysteries right and left. River Heights would be like my own personal little fiefdom.
Sorry Nvme77, I’m Morgaine is taken.
Damned vanity searches…
Kim, from “the Fionavar Tapestry”
she’s smart, she’s pretty, she has a neat ring that lights up and calls dragons…
Just for a while – Emma Peel from The Avengers.
Or perhaps a character from a short story from about thirty years ago. He could control anything that appeared on televisions everywhere.
Mystique…
Without a doubt…just imagine the possibilities
Hob Gadling, from Neil Gaiman’s Sandman.
What’s the secret to not drowning? Don’t drown.
What’s the secret of immortality? Don’t die.
In the year 1389, Robert “Hob” Gadling was in a tavern loudly proclaiming that death was for fools, and he for one wasn’t planning on playing along. He was overheard by Morpheus, Lord of the Dreaming, who turned to his sister Death and said, “It might be interesting…”
After Death agrees, he turned to Gadling and said that, if death was just a game, then he’d meet him at that same tavern, one hundred years hence. Everyone in the room laughed at the way Gadling had been shot down.
(after much thought)
Murdock from The A-Team.
Or, heck, Willy Wonka.
Proginoskes, from Madeliene L’Engle’s A Wind in the Door.
I see several like-minded people here. I was thinking Jo March - not only does she get to write, but she gets the big house in the country, a devoted husband, and all those kids! I want her life.
Then Claire Fraser - an interesting life and Jamie too!
Next it was Morgaine from Mists of Avalon.
But since all those have been used, I’d go for Annie Laurence Darling, who runs a mystery bookstore on an island and has a very rich and charming husband.
Or Stephanie Plum, whose life has its compensations even though her cars do get blown up on a regular basis.
Or Magdalena Yoder, who lives in Amish country in Pennsylvania and runs an inn. I like her because she has a sharp, witty tongue, and who else would have the nerve to refer to Streisand as “Babs”?
I could be content being any of the above.
I’m with TrippyDish. Sure, I’m a guy, but I think it’d be great fun to be a shape-changer like Mystique. Even if it did mean I’d have to get, er, rearranged. (I’d go with the Martian Manhunter, but he is such a square.)
FISH
Sarah Kerrigan from the game Starcraft.
What am I going to do today? Ah, yes, that’s right, raze a planet and breed a few new Overminds… not to mention twiddle with that lovely DNA I got a hold of last week.
Maureen Johnson Long, from Heinlein’s To Sail Beyond The Sunset.
Oo,Oo! Also, Angelina, Slippery Jim Digriz’ wife in The Stainless Steel Rat.
Lando Calrissian.
He’s got an industrial empire built on card games. He owns gas mines. What kind of entertainment do you think is big in mining towns? Gambling and prostitution. If he has the corner on those two markets, then he’s recouping the majority of his workers’ wages.
Don Vito Corleone was pretty cool too. Family guy, very respected member of the community.