I feel your pain. Literally. I have a son who's 20 months and he is going through the same thing right now. I stay at home full time with him, and he tries to bite me or my husband several times a day. He also pulls hair, hits, and throws things at us. He thinks it's funny and laughs when he does it, even though he knows he shouldn't do it. For example, he'll come up and bite us, then laugh and shake his head "no." He has not bitten other kids (yet!), but he does hit and push them. It's very frustrating for me at playgroups. He even ran up to a random kid at the mall the other day and pushed him before I could get to him. So embarrassing! He also is the best little boy 90% of the time, but for the past month or so, he has turned into a bully at times.
We have tried everything - timeouts, taking toys away, ignoring the behavior/not giving him attention, being stern yet calm with him, etc. I don't believe in spanking, so that's something that's not an option. Everyone in my mom's group keeps telling me to just be diligent and keep trying to find some form of discipline that will work for him. I've tried timeouts (for 1 minute), and they didn't really work well because he would just climb out of the chair. Then a friend recommended strapping him in a booster seat on a chair and putting him in another room so he's alone. That seems to have worked a little better, but still not great. He just doesn't seem to mind being in timeout. I just think he's too young to "get" the whole timeout thing. But it may work for your son, so I say it's worth a try. What HAS just started to work for us in the past couple days is taking away his balls. He's really into balls right now, so when he misbehaves, I put his balls on top of the refridgerator. He gets really upset and I think he's finally starting to figure out that he's going to lose his balls everytime he bites/pulls hair/hits/etc. I know you said your son doesn't really have any favorite toys that you can take away from him, but something to keep in mind in case he starts to favor a certain toy.
Unfortunately, I think this is just a hard age to discipline because they can't really make the connection between their behavior and the consequences. I keep telling myself it's just a phase and it will pass. Good luck to you!