Minefields.

I just hope we will be able to have energy weapon variables of the normal defenses like a turret
That shot lasers or plasma I'd like that.

you mean smart mine fields that dont harm settlers or merchants so when you come back you dont find settlers with no legs or dead?

Gatling laser turrets? Now that's something I want in every corner of my settlement!

I would just like to witness a night raid on my settlement and all my turrets light up the sky with there firing and I'll just sit back and enjoy the music of there screams..oh ya thats what I would like.

A plasma mortar/cannon/caster turret would also be very nice...

Boston's skies will not be lit by the rockets' red glare... It will be lit by the plasmas' green glow.

Oh, and if one of the random invasions involve enemy robots or even better, power armored enemies, we could need some EMP wave emitter traps/turrets...

Airship firing hell on everyone else.

Saturnite 4th generation MIRVs launched from scrounged nuclear silos.

You guys do realize some of these defenses you wanted will likely destroy your settlement along with your enemies?

On second thought thought maybe that's not so bad because who cares what or whom get blown up as long as we can blow sh*t up?

An elite squad of deathclaws which I train from birth.

Talon Company

A moat that has sharks with lasers attached to their heads.

Is that to much to frikkin ask for?

I'm fond of sentry robots and turrets, although the ultimate security defense will be me.

Before building your town, I suggest watching Season 2 of The Colony on Netflix.

Basically, my advice to other players, establish a parameter FIRST and build your commodities LAST. That being said, I would most likely establish a tall, octagonal, parameter with a Native American style entrance, (overlapping walls with only enough space for a single body to pass at once) as well as mounted, automatic turrets at every corner and manned turrets at the main gate.
Example: http://i.imgur.com/CPJNvjI.png