* accord and satisfaction;
* action on advice of counsel;
* arbitration and award;
* assumption of risk;
* comparative negligence;
* discharge in bankruptcy;
* duress;
* estoppel;
* failure of consideration;
* fraud;
* illegality;
* injury by fellow servant;
* laches;
* license;
* payment;
* release;
* res judicata;
* statute of frauds;
* statute of limitations; and
* waiver.
M.R. Civ. P. 8