what would happen if I wire a transistor like this?

 

BJT's are not suitable for parallel operation (particularly in linear mode) as you have shown without some form of current sharing control - such as a series resistor of appropriate value in each of the emitter terminals.

 

The transistor with the lower Vbe at a given current will pass more than half the total emitter (collector) current. Since Vce's are equal, the one passing more current will heat up more than the other one, causing it to draw even more current. This is the beginning of thermal runaway. You can mitigate this by adding series emitter ballast resistors which drop around a few hundred millivolts at the anticipated current level.

 

@t_n_k : oh, i see. what values can you suggest? i'll be using a 2n3055 transistor.. what would be the power?

@ron h: thank you