What assembler do you use?

I have been brushing up on my assembly recently. I did learn a bit on dos yeeeears ago, probably with masm. Now I'm using linux. I'm not sure whether to go with the nasm or gnu as.

>>3 Because sticks are free as in Freedom, not proprietary like most lighters. You must reject those evil proprietary fire-starting devices and only use Free ones like GNU/sticks.