I recently purchased a Desert Eagle after wanting one for the last 10 years after seeing it in the movie "Snatch".
Originally, I wanted it in .50 AE because that's the one in the movie and in most of the youtube videos with big explosions.. but I was never able to save up the money to buy the gun on my $10/hr wage.. though I was determined enough 7 years ago (when I worked for a sporting goods store) to purchase 2 boxes of ammo, a holster and the hogue grips in anticipation of buying the gun.
Ultimately of those items, I only have the ammunition remaining.. moving several times since those days and the need to clean out the closet has resulted in the loss of the other items.
I hadn't done much research at the time because having my first "permanent" fulltime job and being 20-21, I was sure I wanted the biggest gun I could get.. and that was the .50 AE.
Thankfully, I could never fulfill that desire due to my other expenses and inability to save enough money to do it.
Several years later, as I have matured a little.. before re-visiting the idea of a purchase, I did considerable research into what the guns are actually used for and the viability of the weapon in areas other than target shooting.
I concluded that target shooting and the possibility of using it as a hunting weapon coupled with my previous irrational want were reason enough to make the purchase. I decided to compromise and start with a 6" barrel chambered in .44 Magnum due to my guaranteed lack of skill in shooting a handgun at long range and the cost of ammunition.
All in all, I can say that it has worked out well. I can honestly say that I've never had more fun shooting a gun than I have with the Desert Eagle.. though my ability to reliably hit exactly where I'm aiming is leaving quite a bit to be desired..
Childish fantasy tempered with realistic compromise is the best way to go based on my experience. If you want that gun you saw in the movie or game, great.. but research it first!