From pre mixed tube
These pre mixed, ready to use Henna tattoo tubes are available in many shops and on many websites. The Henna paste in them will give a good colour. You will have to apply a good amount of pressure to release the Henna and this can make you inaccurate and your hand ache. But they are a cheap and easy way to try out henna tattoos and if you used them with a carrot bag/application cone (see below) you can get some great results. They are available at:

pre mixed tube
application cone
hand rolled cone
jaquard bottle
paint brush

Carrot bags/Application cones
These are great to use either with Henna from the pre mixed tubes (above) or Henna you have mixed yourself. They are easy to use, give you great control and you can cut the nib to the size that suits you. Also re-useable as all they need is a quick rinse when your done. They are available at:

Hand Rolled Cones
You can make these yourself from florist cellophane or purchase them from a Henna store. They are very similar to use as the above carrot bags.  

Jaquard Bottles
This is a very popular tecnique. Though it can take a bit of presure to squeeze the bottle which makes your hand ache. Also you need to make sure your paste is very smooth so that it doesn't clog the nib but on the plus side it will enable you to make very fine lines.

Paint brush
Brushes can be very useful, especially for applying henna through a stencil. You can also use it to paint a design directly onto your skin. This will give a much looser style to your art. It could be useful for painting Kanji.They are available in henna kits at: