One thing hasn't changed much for more than a century: pistols are still the primary service weapon for police officers. Of course, they've gotten much more sophisticated since the first revolvers.
High-powered sniper rifles, like this Barrett M82, have been acquired by police departments in the US. The M82's power allows it to be used as anti-personnel or anti-materiel weapon.
Long rifles have become more prevalent on American streets since September 11th, 2001. This rifle, the Special Operations Forces Combat Assault Rifle (SCAR), can be used both as an assault rifle or sniper rifle. It is used both by militaries and police forces around the world, including the US.
"Riot guns" are capable of launching explosive grenades, smoke grenades, or "less lethal" ammunition. In the wake of 9/11, police departments around the country have received semi-automatic grenade launchers.
Non-lethal weapons like pepper spray are widely used by police forces and have been in the law enforcement arsenal for decades.
In the 1960s, a federal commission on crime recommended that the government explore technologies that are less-lethal than pistols. They spelled out the need for the Taser before it existed. Now, Taser pistols are a popular choice for police departments. They disable people by firing dart-like electrodes that disrupt muscle control. Tasers are not completely non-lethal, and have been implicated in serious injuries and death.
The Taser XREP projectile has a similar effect to Taser's handguns, but can be loaded into traditional shotguns and has a longer range.
The Taser Shockwave is like a Taser on steroids. It is an electroshock "cannon" that allows users to disable multiple people in a crowd.
MRAPs, or Mine-Resistant Ambush Protected vehicles, were developed by the US for use in Iraq and Afghanistan. Many of these heavily armored vehicles were given to police departments across the US when their overseas service was no longer required.
Even regular police cruisers have become more aggressive looking. Some departments have replaced the iconic Crown Victoria with interceptors like the Dodge Charger.