Rising Sh0t is a tier 3 skill in Zer0's Cunning skill tree. It allows each ranged or melee attack to give bonus damage for a short amount of time. This bonus can stack up to five times. Faster weapons gain stacks more quickly, but slower weapons retain stacks for a longer period of time.
Some weapons, like the Skullmasher, will grant multiple stacks from a single trigger pull.
Stack depletion rate seems to depend entirely upon the fire rate of the equipped weapon, regardless of whether you use regular weapon attacks or melee attacks. As a result, weapons with slower rates of fire are more effective for maintaining Rising Sh0t stacks while using melee.
Also by using a weapon with a high rate of fire to get stacks quickly and then switching to a low rate of fire weapon and shooting an enemy causes stacks to deplete slower.
Reload times for most weapons tend to be long enough that you will lose all Rising Sh0t stacks during the process.
As a result, Bandit weapons are often particularly effective for maintaining stacks due to their large clips.
Minimizing reload times when using a weapon with a very slow rate of fire can allow you to maintain stacks during reloads as well; the Killer skill works especially well for this.