Q are ageless, immune to all known diseases, and able to function normally in any known environment. Although they freely describe themselves as "omnipotent", the Q definitely have limitations, one of the most obvious being other Q. Q can combine efforts to harm other members of their race or even deprive individual Q of their powers.
The Q normally dwell in an alternate dimension which is supposedly incomprehensible to humans. Human visitors subjectively interpret their experience of the "Q Continuum" based on prevailing conditions in that realm and their own cultural background.
Although it's not clear exactly what "Q weapons" were provided to the crew of the USS Voyager, collateral damage from the Q "Civil War" caused an abnormal number of stars to go nova in the Delta Quadrant of the Milky Way.
Q interests regarding the human race are normally handled by a single representative. This individual has a history of insulting, tormenting, taunting, and otherwise harassing races all over the Milky Way.
Q does not frequently appear as a contender in debates, although he is sometimes used as an excuse for a confrontation to occur. Occasionally, however, a trekkie will make the argument that even if the Galactic Empire were able to defeat the Federation, Q would come to their rescue (oblivious to the fact that Q has never come to their aid in any crisis that he did not instigate himself), effectively conceeding the real question of whether the Federation stands a chance against the Empire in a military conflict.