It appears the occupation forces on Japan proper had little opposition. However, on many of the islands where the Pacific war was fought, sporatic opposition by Japanese holdouts continued for many years. Here's a website that appears to be a pretty good registry of Japanese holdouts. Here are some examples:

January 25, 1946 - Mountain Battle between Filipinos and Japanese
On January 25, 1946 a Japanese unit of 120 men was routed after a battle in the mountains 150 miles south of Manila. The Japanese were armed with small arms and at least one light machine gun. 72 were killed by a Filipino battalion, led by American "Black Hawk" 86th Infantry Division. The survivors were tracked down and most were apprehended.

February 22, 1946 - Lubang island Allied casualties in a post WWII battle
Intense fighting developed on February 22, 1946 when troops encountered 30 Japanese. Eight Allied troops were killed, including 2 Filipinos. The Filipino and Americans sent for an additional 20,000 rounds of small arm ammunition, but not future battles occurred of this magnitude. In early April, 41 members of the Japanese garrison on Lubang island came out of the jungle, unaware that the war had ended.

March 1946
A Japanese band of unknown size attacked and killed a six man patrol on Guam.

March 1947 - Ei Yamaguchi's Band Attacks US Marines
Peleliu is a small six mile long by three mile wide island. It was originally secured by American Marines in November of 1944 after fierce fighting. A band of 33 Japanese soldiers renews fighting on the island by attacking a Marine patrol with hand grenades. At that time, only 150 Marines were stationed on the island, with 35 dependents. Reinforcement were called in to hunt down the hideouts.American patrols with a Japanese Admiral sent to convince the troops that the war was indeed over finally convinced the holdouts to come out peacefully.

Private Kinshichi Kozuka -(age 24 in 1944) Killed by two shots fired by local police on October 19, 1972 when Kozuka and Onoda burned rice that had been collected by farmers, as part of their guerillia activities.