To me, Tsonga has the most aggressive game of all active players. His shot making screams an end-the-point-now intent, from groundstrokes to the volleys to the dropshots to the serve/return. he isn't that patient and often does not take on a defensive position until forced to do so. Gulbis is much like tsonga in this regard but, well, i haven't been able to see him play often to say anything from my POV.
Davydenko is aggressive, but I don't think he fits the stereotypical aggressive player. I would much like to think, although he has the ability, the power he injects to that aggression depends more on the opponents power than his own. aggressive counterpuncher i guess as opposed to the monfils/simon types.
Llorda on the other hand, i think is aggressive because he is fairly lacking in the defense department, which gives him no choice. add to that the old-school serve and volley tactic and viola.
berdych has very strong groundstrokes, which imo, is not automatically an indication of an aggressive game (see delpotro), plus he is lacking on all other aspects beside serve/return and grounstrokes such as netplay and [aggressive] touch to see him as trully aggressive. This may come off as unfair but i actually think he's a ballbasher which is undeniably aggressive, but it's just because of his easy power, not exactly because of an aggressive mentality.
Which brings me to this question, is being a ballbasher/power baseliner the very definition of an aggressive game? if so, we really have very few in the men's game.
And also, shouldn't Wawrinka be there?