Think about it. What do you want to do when you see a diamond ore but it is surrounded by a bunch of mobs? With my idea the answer would be blast them all and then take the diamond. This lazer could be upgraded but is crafted by putting a button in the middle of a workbench, above that a dispensor, to the right of that a glass and to the left one iron bar above another iron bar.

When you craft it it is a ranged lazer pistol with the strength between iron and diamond swords. But by aquiring new parts from different things you could make it stronger with different features. For example, put the gun in a workbench with a diamond and 3 glass and it becomes stronger. Other upgrades include:

• Craft a blaze powder in a diamond shape made of glass to make a flame orb. Craft a flame orb and a lazer gun to make a gun that shoots flames.
  
• Craft TNT and a lazer gun to make an explosives gun. (TNT is ammo)
  
• Get a non upgraded gun and craft it with an emarald to make a mining gun. (This can then be upgraded with the upgrades the normal gun can have.)
  

There would also be a rare new hostile mob called the Alien. It would shoot you with a lazer gun for 1 heart of damage per hit. It would drop slimeballs and rarely it would drop a lazer gun (they can drop upgraded lazer guns.)

So thats my idea, I hope you like it!