A false dilemma is a logical fallacy in which a set of options are presented as if they are mutually exclusive or as if they're the only possible options, when in fact they are not.  It is used to give the impression that if one rejects another's argument, he must necessarily embrace an absurd or unappealing stance.
A false dichotomy is a special case of a false dilemma, in which only two options are presented. One side of an argument presents to the other two unpleasant, opposite, and extreme alternatives, alleging that they are the only choices open in the matter up for debate. The fallacy lies in disregarding the middle ground, or failing to credit the range of disagreement on the issue.
The all or nothing fallacy assumes that things must be completely one way or another.
- ... it is part of the most primitive of human responses: The Fight or Flight Response. When faced with a life-threatening situation, we must make a snap decision and act on it. There is no time for 'maybe this', or 'maybe that'. Either decision will create an emotional reaction to allow us to fight or flee to the maximum of our ability. 
Academics call it the "bifurcation fallacy".
Of course, not all dilemmas are false dilemmas. Also, a false dilemma should not be confused with a reductio ad absurdum.
The false dilemma is the opposite of the middle-ground fallacy, the fallacy of assuming without justification that a middle position between two extremes must be correct simply because it is the middle position. Both arguments are fallacies because the mere existence of two extreme positions says nothing about the existence or the rightness of the middle ground.
- "Either you're pro-life or a supporter of the death penalty." — This is not a contradiction, since Christians can trace both positions to Scripture (Exodus 20:13 and 21:23, respectively). The distinction is obviously one between killing an innocent and inflicting justice upon a criminal, yet liberals use this either to accuse the Bible (and consequently, God himself) of inconsistency or to support their position against capital punishment.
- "If history as depicted in the Bible cannot be supported by empirical evidence, it must be false." — Another obvious fallacy, since a) nobody can rule out future discoveries that would corroborate the Bible; b) all "evidence" humans can possibly obtain would be a bad measure to check divine revelation; and c) misunderstanding and misinterpretation on the part of humans would doom any such effort.
- "If you oppose Barack Obama/Hillary Clinton, you're a racist/sexist!" They are false dichotomies because they ignore many possible reasons for opposing Obama/clinton.
- "If we allow that activity, then everyone will do it, to the exclusion of activities that we need to have happen." — That collectivist argument ignores the possibility that enough people will still be left to do the needed activity, as well as the possibility that some people will do both.
- Depression:Understand it, Treat it, Beat it
- Exodus 20:13, "Thou shalt not kill."
- Exodus 21:23, "And if any mischief follow, then thou shalt give life for life..."