DO NOT PLEAD A LAUNDRY LIST. The vast majority of these affirmative defenses will not apply to any given case–they are intended as a brainstorming tool, and certainly should not be included in full. Rule 11 requires that you have a good faith basis for believing an affirmative defense actually applies before pleading it, and in discovery you will likely need to respond to an interrogatory identifying all factual bases for every affirmative defense you plead.
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List of Affirmative Defenses (Partial):
– failure to state a claim upon which relief may be granted (almost always use)
– statutory defenses prerequisites (these will vary depending on the claims)
– preemption by federal or other law
– accord and satisfaction
– arbitration and award
– assumption of risk
– economic loss rule
– contributory or comparative negligence
– intervening cause
– supervening cause
– claimants own conduct, or by the conduct…

Here’s a tip for all you tax payers out there: Donating money to help reduce the federal debt counts as one of the more unusual charitable tax deductions.