How do i deal with an out of control 2 y.o. that doesn't mind time outs?

i have a 2.5 y.o son who is just consitently getting into trouble...purposely i think. he's become very aggressive by hitting anyone and everyone when he doesn't get his way. he's in time out at his pre school almost everyday for not listening. my husband and i just don't know what else to do!! for timeouts we first tried a chair. that didn't work. he would just sit htere and hum. then we started putting him in his room. he would just start playing wih his toys. now i find myslef with little to no patience with him at all times and i feel like i'm constantly yelling at him. the worst thing is that when he does soemthing he knows he's not suppose to, he'll look inour direction and give us this smirk that says " i just wanna see you explode". aaagggrrrrhhhh!! any advice??