One very important light modifier used by photographers is the snoot.
A snoot is basically a cone placed in front of the flash to direct light into a concentrated area. Some snoots have honeycombs that basically softens the edges of the light so you get a softer light falloff. You can also put colored gels in front of them too.
I use the snoot to create highlights on areas of my background so it doesn't look so plain.
I have one of those really cheap ones that you can buy online made of aluminum. With these you have to be very careful especially when using your modeling lights as these can get really hot, hot enough to melt the plastic parts of your studio lights. You can actually turn the modeling lights on to aim the snoot, then turn them off when you're ready.
I've also seen a lot of do it yourself snoots online made of cardboard or plastic. There really isn't much to them, they are just cones, so if you can make one then go ahead.