In Mega Man 2 you go around destroying Robot Masters and collecting their special weapons to use against them, pretty standard Mega Man stuff.

Now, each weapon takes a certain amount of weapon energy, represented by the meter to the left of your health

Several of the weapons take significant chunks out of your energy meter, but some, like the Metal Blade, give you several shots per bar of energy. You can use this to your advantage.

First, equip something that drains less than one bar of Weapon Energy per shot, like the Metal Blades or the Quick Boomerangs, then start firing. Before you consume the first bar of weapon energy, bring up the weapon selection screen by hitting Start.

Then immediately close it. That fraction of Weapon Energy you used? It gets reset! Meaning that if you keep bringing up the selection screen after every few shots, you'll never run out of Weapon Energy for those weapons.

Of course you have to constantly count how many shots you've gotten off, and pause the game every few seconds, which makes this really tedious to do.

But it's totally worth it, right?