Zymic

Open up the image you want to use, I used the one below:

We are now going to use a filter called the liquify filter, if you have v. 7.0+ you should have it. [ Filter > Liquify ] and make sure you have the hand tool selected and the below brush size:

Now we can have some fun, place the brush underneath her nose and drag up to give her a little piggy nose. Experiment until you get her nose as ugly as you require!

Now the eyebrows, again using the same tecnique above. The hand tool simply drags and stretches parts of the image and makes it look pretty realistic.

Now for more parts of the image, simply experiment and drag parts of her face and make her really ugly! Make her face fat, stretch the lips etc.

Experiment with various tool's, use the decrease tool and make her right eye smaller like below.

Now increase the size of her left eye!

Now simply experiment and use any other tools you wish, the liquify tool is great for lots of things.. use various other tool's in Photoshop too! My result is show below: