Most moders like to have 2,Ohm or less so the MOSFET doesn't get too warm because of the limited cooling. The currently recommended MOSFET's I've seen include IRLB3034PBF, IRLB3813PBF, PSMN1R9-40PLQ, and the newest addition of the PSMN0R9-25 (surface mount) which is what I use on the 'microFET' board I sell on eBay which also include the pulldown resistor and very easy to install.
An early one people liked but have been moving away from more is the IRLB8743PBF, but in a series build this is still a possibility, just not as good for parallels as the others.