My vote would be for a full metal except for grips replica revolver in .22 caliber that delivered at minimum 400 FPS with 14.3 gr pellets for at least twenty shots. According to the particular real steel design I'd want it to hold exactly as many rounds as the original.
A replica of the 10 shot S&W 617 would be fine and appeal to most younger shooters.
For more classic six shot cylinder designs grips should at least look and feel like those found on a factory unaltered revolver. Wooden grips should be a factory option.
Several presently available replica airguns would meet my criteria except for caliber and velocity in that caliber.
I presently have a 38T in .177 and a Crosman 357 first model I restored to working condition. Both are accurate and the equal of newer designs in velocity, but neither is as satisfying to shoot as my old 38C in .22 was even with its less than stellar velocity.
My rebuilt S&W 78g puts a 14.3 gr pellet down range at well over 400 FPS thanks to the new Mac 1 Hot Valve. Very accurate and with the feel of shooting a real steel gun.
Its a great gun, no longer in production of course and a single shot.
So what would be your pick and why?