tit for tat
EFFECTIVE STRATEGY IN GAME THEORY FOR THE ITERATED PRISONER'S DILEMMA
Tit-for-tat; Tit-for-Tat; Tit for Tat; Tit for two tats; User:Volunteer Marek/WikiPhil; User:Radeksz/WikiPhil; Tip for tap
Give and take, blow for blow, a Roland for an Oliver, measure for measure, diamond cut diamond, equivalent (in retaliation), quid pro quo.