Addon: Rocket Launchers, Landmines, Miniguns and Laserguns!

You can get these bad, bad boys from your local weaponsmith. Neat, hey. Level the trader all the way up and the final top-of-the-range trade will be an enchanted axe. Nice! Boring! Not that nice! How about landmines or miniguns??!? You betcha. Just make sure you bring yo emeralds. And emerald blocks!

Laser Guns

Fairly underpowered compared to the various other turret weapons, they are also cheaper (and more fun!). They will drop their spawn egg if the player destroys them. If they are destroyed by monsters, they do not drop. 

Armor-Piercing Rocket Launchers

Not too sure if these even exist in real life! But who cares, we're not here for reality. These will go straight through a line of monsters, you just need an orderly line of monsters and these rocket launchers will take it from there. Cooperation, people. 

• Buy them from your friendly weaponsmith. Unfriendly weaponsmiths probably sell them also.
• They don't break blocks (it's a kind of magic).
• They drop their spawn egg when destroyed.
   

Rocket Launchers (normal blowy-up ones)

Place these things down and, just like the minigun, it will target any monster. Unlike the minigun it will replace the monster with a very large hole in the ground. Use with CAUTION.

Also available from your local weaponsmith. Slightly cheaper and tougher than a minigun but quite destructive, so will wreck the landscape quite a bit. When they're destroyed you can pick them up and place them back down. So, not all that 'destroyed' when you think about....
 

Landmines

Block Breakers (red light)

Place them down, and you have five seconds to get out of the trigger-zone. After that, if anything comes within a few blocks, there'll be a boom. And that anything might be gone. As well as a good chunk of land. For reference, they do about the same damage as a charged creeper... Ummm, maybe don't place them near your base.

Craftable: 

Non-block Breakers (yellow light)

As for the above, but no breaking of blocks. Consider them your personal anti-personnel mines. Cheaper and easier to trade for.

Craftable: 

Miniguns

These are all sorts of nasty. Place one down and it'll shoot any monster. Many times. Not a whole lot of hit points but you can repair them with iron and when they break you can just pick them up and place them down again. Now available in a range of colors to match any decor.