The green laser pointers are the ones idiots used to blind pilots in flight, and there was discussion here in Germany to have them banned. They tend to be very intense.
I agree with tim away, a pointer leaves a better impression for me: it lets the presenter look more dynamic, you have something to do with your hands (very important, since I always catch myself wantign to put them in my pockets!), and you force your listeners to look away from you (i.e. short relief).
Of course this isn't appropriate if you are sitting at the back of the room...
“Strange women lying in ponds distributing swords is no basis for a system of government. Supreme executive power derives from a mandate from the masses, not from some farcical aquatic ceremony!” Monty Python and the Holy Grail