Markers

For drawing on the balloon, I have used dry erase markers, permanent markers, and paint pens. I’ll explain how each is different.

You can pretty much use any permanent marker to draw on a balloon. The most common color you’ll usually need is black.

Permanent markers (especially Sharpies) are so common and easy to find in stores in a variety of colors.
I prefer the BIC Mark-It pens over the Sharpies, because the BIC Mark-It pens actually say they are acid-free, and so you can also use them on photos and other things too. (The acid from the ink can cause your balloon to deflate prematurely.)
Permanent markers look quite nice and bold on the balloon.
If I am twisting for kids, I prefer using dry erase markers. With permanent markers, if the balloon is popped, the ink isn’t quite so “permanent” and can rub off. (But it usually doesn’t really matter.)
My newest find are the Cra-Z-Art markers. They are acid-free, the metallic colors are quite nice, and they can be washed off with soap and water.

BIC Mark-It Markers Fine Point, 36 Markers	BIC Mark-It Markers Ultra Fine, 36 Markers	Sharpie Markers Fine, 24 Markers	Sharpie Markers Fine, 5 Markers Retractable
Cra-Z-Art Markers Metallic colors

Dry erase markers also work quite well on balloons.
The reason I prefer dry erase markers (over permanent markers) for kids is that if you pop the balloon, the ink won’t rub off.
I like the fine tip Expo markers for more precise drawing.

Expo Dry Erase Markers Low odor, black	Expo Dry Erase Markers Low odor, fine tip	Expo Dry Erase Markers Low odor, fine tip
Expo Dry Erase Markers Low odor, fine tip	Expo Dry Erase Markers Low odor, fine tip

If you want to draw on dark colored balloons, you’ll need to use a paint pen.

I often use them for drawing eyeballs.
I’ve tried a couple paint pens and am still figuring out which one I like best. Currently, I prefer the Elmer’s pen because it is acid-free, but both have worked fine.
You can usually find these pens in craft stores.