Depending on the distance to your target, that would likely be an Olympic style target pistol, such as a Hammerli or Pardini FPE. For ranges of greater than 50 meters, a bolt action pistol in a rifle caliber would be a good candidate. Many can trace their origins back to the Remington XP-100.
Both can be equally accurate
The most inherent accuracy will be found in bullseye target guns, such as a Smith 41.
Telescope
Factory, I'd probably say the 500 Magnum
Mine are very accurate to about 50 meters.
Blue Book of Gun Values
"Best" is too subjective to define for a hand gun. The biggest, the most practical, the most accurate, the most concealable, and the most durable pistols are all totally different guns. Two very popular models are the 9mm Glock and .45 caliber 1911. Both are used extensively by law enforcement and military personnel.
The question can't be answered as written.
Super soaker 8000
Value is too difficult to be accurate without seeing the gun. Condition which includes the amount of original finish and original configuration will determine value. Recommend taking it to a gun shop for appraisal.
Right hand "a gun". And left hand "the World"
Not even close. There are several more powerful handgun cartridges, not counting the single shot pistols that use rifle cartridges. While Dirty Harry may have proclaimed it to be "The most powerful handgun in the world"- it is not.