I'd say no.
I had a player like that over a year ago. It doesnt just stop, he or she will continue to ask for rediculous things that they know better than to get.
For instance I had a player literally ask to be Squall Leonheart from FF8 in my Forgotten Realms game. This was after he asked if the Lantanese could make a Sword with a Gun the Hilt. I said no and the crazy requests kept on coming.
If you say yes, they ask for more stuff.
If you say no, they ask for more stuff.
If they're going to keep asking for stuff anyway, why not find a way to give it to them? At least then they're happy.
"You want a gun-sword? Sure thing. This little beauty here may look like an ordinary flaming greatsword, but there's actually a flask of concentrated alchemist's fire in the hilt, and when you hit this switch, it comes boiling out to cover the blade. When you hit these two switches together it sprays out a burst of flame and then the safety interlock cuts in, but you'll melt the conduits if you use it more than once a day. Don't bother refilling it, just stick the hilt in the embers of your campfire once a week or so and it'll take care of itself. How's it work? Ha ha, my lad, that's what you pay ME to know!"
And there ya go. That's your standard 4E flaming greatsword in terms of price, properties, and bonuses, or you could get all esoteric and swap its MIDaily power for 1 cast of burning hands applying the weapon's item bonus to attacks and damage, though it'll probably be rather inaccurate due to your average fighter intelligence bonus.
I mean, look at the worst-case scenario here. If you give one player what he asks for, maybe your other players will start asking for things too and expecting to actually get them.
And then instead of spending your time coming up with giant elaborate plots that your players aren't guaranteed to blow off to look at some insignificant detail, you can just take a little time to look at the wish lists, see what looks good and how you can link it together, and watch their little faces light up like kids at Christmas time.
My god, how could anyone ever put up with that?