I am very sorry to hear what you and your son are going through. I'm sure it's very difficult but there has to be a reason for his behavior. I really don't have any experience with this but I do remember some time back seeing an article about children with similar behaviors and a connection with that to specific food allergies. Here are a couple website that might shed a little more light on the subject. I do think it would be best to take him to his pediatrician and see what he/she recommends or suggests. I wish you all the best.

http://borntoexplore.org/allergies.htm

http://www.garynull.com/documents/nutrition&mind/nutrition&mind-7.htm

Pardon me if some of these are obvious questions...

but

Have you made any connection between the onset of his anger and any environmental issues... such as changes in your relationship with his dad, exposure to anger and violence of others, etc...?

What do you do to discipline him? I know that the challenge of finding an effective discipline approach can be daunting, especially when we are already in the throes of dysfunction. SO let me suggest two wonderful resources which may help you.

1,2,3 magic by dr. phelan. this book is great if you do what it says TO do and don't do what it says NOT to do. Its more than just counting and time out, but you have to be consistant, and really heed what he says about your own emotional responses and withholding 'talk'... check it out, it even works with children with learning disabilities and ADD... its a behavioral modification approach which is geared at ages 2-12, but the earlier its put into play, the better, for obvious reasons... habits of reactivity become more ingrained over time... so don't procrastinate.

also

Scream free parenting by runkel. and this title can be deceiving, as the book is NOT geared to people who raise their voices, its about modelling self control, and the different ways which we undermine and frustrate our discipline by trying to control the kids rather than by guiding them into better choices. Its also about the power that we give them when we overreact or when we let ourselves be pulled off balance by their behavior. A priceless book for any parent, regardless of the challenges. Honestly, I think its a good resources with wives whose only child is the one they married, too, lol, but I digress.

I totally understand the desire to not get into the label game...

and I agree that sometimes food allergies can be amazingly underestimated and underdiagnosed, especially when it is more of a sensitivity to something which impacts behavior as opposed to a full blown allergy that manifests with obvious physical symptoms. Even it is is a food allergy or other organic issue, the books I mentioned will still be great assets!

der, do you read typonese?

not "even it is is" but

EVEN IF IT IS...

At 2 1/2 he should not be too young for testing. I think they can begin testing at 2 years of age. I know you do not want him "labeled" this young but you have to keep in mind that he probably does not want to be this way and as angry as he is he is not able to enjoy being a little boy. Once evaluated he could qualify for services such as behavior modification and social group. This will help teach him how to interact with children so he does not just sit by himself. I am not sure where you live but the birth to 3 program can evaluate him for any developmental, social or other problems he may be having.

im glad to hear you have this prob cos i have a 1yr old she is very advanced for her age and she has days where she will just play with toys them for no reason she starts throwing them and me or will just hit me in the head with them and loughs or she will spit at people or when ever people say her name she will say na realy loud and hit them the worst thing she had done is bite my 5yr old and drew blood she sat on her and bit her ear oh and if you ask for a cuddle she will hug you then pull ya hair i just dnt no what to do with here i think she is to young for a norty spot but saying no or pretending to cry when she dos things dnt work she just keeps doing it my 5yr old was never like that as a baby she even hits our cats

I think the book suggestions are great. Another thing to remember is that often they are so young when they get frustrated over something, they don't know how to vent this anger other than to lash out. I think trying to stay calm during this time is the hardest and yet important thing to do.
This is a trying time for us mothers and don't forget to get your time and things you need for you in order to help you stay calm and patient through these challenging stages.

If I were you I would get him seen by some sort of proffessional, as the longer some things are left unchecked, the worse the problems can become. For everyone's sake tho, I do hope it is just a phase & not some other problem.