You mean altering the size of the bullet, I assume? I believe this is tied to the font-size of the li tag. Thus, you can blow up the font-size for the LI, then reduce it for an element contained inside. Kind of sucks to add the extra markup – but something like:
li {font-size:omgHuge;}
li span {font-size:mehNormal;}
Alternately, you can specify an image file for your list bullets, that could be as big as you want:
ul{
list-style: square url("38specialPlusP.gif");
}
See: http://www.w3schools.com/css/css_list.asp