In Star Trek: First Contact, the crew begins to use rifles when they battle the Borg on their ship. A bit later in the movie, Picard tells Lily that the phaser she had pointed on him was set and maximum and would have vaporized him.
If a hand-held phaser can vaporize someone, why would they need one the size of the rifle? Bigger power cells? More ability to make the phaser modulation randomize (wow, I almost sound like a Trekkie there, don’t I? 
)? Some other reason? No reason at all?
So that Worf would look cool chucking a rifle at Data, who grimly catches it? I think that’s the most likely explanation. Worf also looked cool smacking that one Borg in the head with the rifle butt.
No, they had phaser rifles in TOS, too. So it couldn’t have been the ‘coolness’ factor.
Well, it could, be we’re trying to work within the continuity here.
I’m figuring they either held more charge or had a longer range or something.
To vaporize two people? 
The Phaser Rifle has been around before First Contact, really.
Some things are harder to vaporize than others, y’know.
If I recall correctly, the tiny handhelds that look like TV Remotes are Type I Phasers; the pistols are Type II, and the Rifles are Type III.
In TOS, the explanation was that the rifles had bigger power packs, and thusly could fire longer.
Extra Geek points: The first appearance of the phaser rifle was in the episode “Where No Man Has Gone Before.” 
There is no reason ever stated for the different kinds of phasers seen in the series but **Jonathan **and silenus’ conjectures are the most likely. Just a bigger battery and higher energy output. One seeming specialization of the rifles is that they can fire pulses whereas the Type I and Type IIs are strictly beam weapons. Not sure what kind of advantage that would possibly give though.
Wasn’t that also the last appearance of the phaser rifle in TOS?
IIRC, Spock was going to use a phaser rifle to kill that one crewman who was rapidly developing god-like powers.
Yes. They showed up in a couple TNG episodes prior to First Contact though.
And the crewman was Gary Mitchell, Kirk’s best friend, Diceman.
It seems to me that in the confines of the ship, pistols are a better choice than rifles.* Also, since the Borg adapt and have shielding to stop phasers but they never develop shielding to stop a phisical attack, why not have Worf use that batlef (yes I know that is misspelled) and replicate some of those Tommy guns Picard uses in holodeck.
*I have never actually been in a battle for a space ship using energy beam type weapons.
The Borg would have adapted to the bullets eventually, just like they adapted to the phasers. If they were particularly susceptible to kinetic energy weapons, Picard would have told the crew beforehand… instead, he just used their (temporary) unfamiliarity with the weapons to kill the drones.
The Security Officers complained that stopping intruders with little dinky firearms that felt like TV remote-controls didn’t give them enough job satisfaction.
Ah, so they just felt more badass with the rifles. I understand now.
They would have probably developed organic Kevlar or some such thing.
If so, then you’ve got to wonder why they didn’t bitch about not being allowed to carry them on suicide, er away, missions.
More on phasers.
Which Type are the phasers that look like Dustbusters on TNG?
Forget guns, how about a freakin Samurai sword, bayonet or even a pointy stick? People in this thread are speculating that the Borg would develop some form of Kevlar body armor to defend. Well, unless they covered up their entire bodies, it would have been better than shooting phasers to make pretty lights when it hit the Borg.
Here is the question that has long bothered me about the Borg. In TNG, the Enterprise crew transports into the Borg ship multiple times, at one point shooting around the ship to cause damage and make the ship stop. My problem is, if you are going to enter the enemy ship to cause damage, how about using something a bit more powerful, like an H-bomb.