Here a few things that I consider necessities in any educated horse person’s “tool box”:

Rope Halter
You may have heard it said that a rope halter has more “bite”, etc. to it because the knots are positioned to apply pressure to “sensitive pressure points” of the horse’s face and nose.  This is not particularly true.  The knots of the halter are where they need to be to make it a sufficient tool. 

They sit soft and loose on a horse’s head until the horse pulls against the halter.  Then, because pulling against the small-diameter rope is not comfortable, the horse is encouraged to soften in whichever way necessary. 

I don’t have much use for flat halters because they are wide and, obviously, flat.  When a horse pulls on these, it doesn’t really encourage them one way or the other.  It’s also hard to offer a nice feel down a lead rope that’s attached to a brass ring.

12 Foot Lead
There are a lot of advantages to having a nice 12-ft. lead, generally with a popper on the end and tied to your rope halter. 

The main reason I use these is because they allow you to move your horse around you without being crowded, and yet you are close enough to easily direct the movement. 

Snaffle Bit
I prefer a D-Ring or an Eggbutt.  They hinge more than slide and thus have less chance of pinching or irritating the corners of the horse’s mouth. 

I use these snaffles because they work off of direct pressure.  They communicate exactly the pressure and release I apply in my hands, no more and no less.  

Bits with a shank, port, twisted wire, etc. work on the horse’s mouth differently and I call them “dishonest”, in less educated hands that is.  The pressure you might think you are applying to your reins can be greatly increased, decreased, and manipulated to apply pressure in the horse’s mouth a totally different way than you what you may have intended. 

Until a person is more sure of feel, timing, and balance in their rein management, a simple snaffle is generally the safest for both the rider and the horse.

Mecate Reins/Slobber Straps
I use mecate reins because I like the feel of them.  They easier to manage and weightier so that they communicate a clearer feel of the pressure and releases I apply to my reins.

Some links to find these tools at competitive prices and great quality:
www.houlihanhorsegear.com
www.lostbuckaroo.com
www.doublediamondhalters.com