Really nice work Sean and Mr.Squeelerz. Sean, you should try working with charcoal. I can tell by your style of shading that you'd be good at it. They sell various types of kits ranging from a few bucks to ridiculously expensive. There's different types of charcoal mediums too. You have vine and willow mediums which are soft and expensive. They're good for really light detailed work, but they don't last very long. They have charcoal pencils which come in various hardnesses. These are good for sharp lines, but they dull just like a regular pencil and you have to keep sharpening them. And then there's my favorite, compressed charcoal sticks. These come in different hardnesses too, I usually get a medium to hard as they tend to last longer and it's easy to achieve an absolute black on the paper. They sell charcoal powder too, but that's pretty much what I do with the compressed stick anyway. I grind it into the paper, usually on the darkest spot of the drawing, and then I move the powder where I need it.
Depending on the grain of the paper, charcoal will flow differently. On cheaper newsprint paper(see my tiger drawing), the grain is really fine and the charcoal doesn't bite into it as well. Cheap paper doesn't give you a very rich or dramatic product like the coarser drawing paper does. The coarser the paper, the better it bites and the easier it is to add/remove charcoal.
And finally, you want a few different types of erasers. Removing material plays just as big of a part as adding material when it comes to charcoal drawings. There's a difference between erasing and removing material. In some cases, you'll find that you need to lighten an area while in other cases, you may need to take it back down to bare paper. I've found in nature drawings there's very few sharp crisp lines. Most things are rounded or blend together. Therefore, when you remove material, you may want to choose one type of eraser over another depending on the job. NEVER use a pink eraser. Those are made for writing, not art. I use a kneeded eraser. These are made of stretchy rubber. You can kneed them into a ball or whatever shape you're comfortable with. When they get dirty, you can wipe them off or simply stretch it out and kneed it back together like a piece of bubble gum. Kneeded erasers are good for removing the majority of material without tearing up the grain of the paper. If you want a really sharp line or if the kneeded eraser isn't effective enough, you can use a hard eraser. These are usually sold in the same shape as pink erasers, but one half will be white and the other half will be gray. I usually use the sharp edge on the white side and then very lightly use the edge on the gray side. The gray side will tear into the grain of the paper if you're too rough.
If you look at the whiskers on my tiger, you can tell I used an eraser. Another option would've been to use white or gray charcoal. I always keep a piece of white charcoal in my box for this very reason, but I don't know why I didn't use it. White charcoal would've came in handy on the eyes, whiskers and around the mouth of the tiger.
Anyway, that's my art lesson for the day, lol. You should try playing around with charcoal. You'll be surprised at how easy it is and what you could do with it. Just like anything, it can get expensive, but a real artist can probably make do with a piece of kingsford and a brown paper grocery bag