Hale's razor. He's the only truly bald one on the team. (Lee and Toll have head stubble.)
Ross' raven-on-a-skull tattoo. One guy mistakes the raven for a chicken, but if you look at it from a greater distance, it also resembles an exaggerated combover - a nod to most of the cast's advanced years. The logo also appears on end of their plane, as the symbol of the "Global Conservancy".
When Booker saves Barney and Co. from the ambush, notice how when he first appears, he only has a machine gun at his disposal, and no rocket launchers. At first this seems to be an error, as tanks cannot be blown up with bullets. Then you realize who plays Booker, and the fact that he doesn't need a rocket to blow up tanks.
Or he just used a disposable rocket launcher. Also, his G36C is also used by the Sangs, meaning that he has a near-endless supply of spare ammo that he can loot from the dead bodies - all he has to do is reach down and pick up preloaded mags, as opposed to reloading his own magazines by hand.