Which voting systems do not have tactical voting? Specifically, expressing your true preference on a ballot will not result in a less favorably outcome.
I'm looking at both multiple-winner and single-winner.
One that I know off already is random ballot, and dictatorial.
As @Watson pointed out, any Pareto-satisfying voting rule that is strategy-proof must be a dictatorship (i.e. one ballot determines the election, regardless of what any other ballots say.)
However note that there are dictatorial voting rules that many would argue are nonetheless "fair" in some sense. Consider the "random dictator" method: Select one ballot at random, and use that to determine the election. Everybody has an incentive to vote sincerely (in case their ballot is the one chosen) and the method is likely (though not guaranteed) to pick the "best" candidate in the sense of maximizing global utility.
By Gibbard–Satterthwaite theorem, any resolute voting rule that satisfies Pareto and which is non-manipulable (i.e. doesn't have tactical voting) is necessarily a dictatorship. See theorem 3.1.2 in Social Choice and the Mathematics of Manipulation by Alan D. Taylor.
