I have heard my leos hiss once, but I've never had them strike at me, or show any sign of being aggressive -- they just run away if they don't want me near them.
Have you been handling your leo on a fairly regular basis? Short periods every day or 2 to get them used to you, and then once they calm down (which sometimes won't happen until they're older, young leos can be a bit skittish) you'll be able to handle them about as much as you like [img]modules/Forum/images/smiles/icon_smile.gif[/img]
I've been having the same problem with my baby beardie actually -- he's my first, and I had been pretty much leaving him to his own devices, because he was very young when I got him and I didn't want to stress him out. Well, I created a monster. He DEFINITELY hisses at me every time he sees my hand now, and he can and will strike and bite. Luckily it doesn't hurt (yet), but I'm doing my best to tame him again... he was so sweet when I first got him, he'd just sit on my hand no problem... If your leo continues to show aggression, try handfeeding (or with feeding tongs) some crickets or mealworms -- that will get him associating your hands with good things...
Jen
[addsig]