Rage meter

Related:
* Finite energy
* Super mode

Has varying names besides the one mentioned in the title, such as fury, bloodlust, charge, adrenaline, etc. and many pick something more unique or fitting for the setting, such as insanity meter. The effect is largely the same, however: brief increase in power/effectiviness gained from being successful in combat.

Getting beaten up may also charge the same meter, but usually not, and most of the time when it does, the charging is much slower than bashing people yourself.

Example effects:
* Allows use of abilities that require rage to use at all.
* Empowers abilities.
* Unlocks supermode.
* Passively increases efficiency, especially if this gradually increases.
... these can either become available as soon as you have "sufficient" rage, that is they can be activated early, but can either be used longer, more often, or are even more powerful if rage is allowed to max.

The rage meter often dissipates after some moments of not charging it up, making it available only a limited time and can't be pre-charged, though this is not always so.