Here are a few accounts from Joseph Fontenrose's The Delphic Oracle, in which he chronicles both historical and improbable oracular responses. The first three are historical and the second two are not. Often, the historical responses are merely a sanction of plans ready to be put into action. Visitors asked questions ranging from the topics of world domination to mundane household affairs.

Historical:

Visitor: King Agesipolis of Sparta
Occasion: Argive proposal of a truce when the Spartans are about to invade.
Question: Is it sanctioned not to accept the Argive truce, which they offer not at a proper time but whenever the Spartans intend to invade?
Response: It is sanctioned not to accept a truce unjustly offered.

Visitor: Halieis
Occasion: A sacred snake of Asklepios was carried unobserved in the wagon which brought Thersandros, uncured of consumption, back from Epidauros to Halieis, where the snake cured him.
Question: What should they do: take the snake back to Epidauros or let him stay where he is?
Response: They should let the snake stay there, found a temenos of Asklepios, make an image of him, and place it in the sanctuary.

Visitor: Isyllos the poet
Occasion: Composition of a paean in honor of Apollo
Question: Is it better that he inscribe the paean?
Response: It is better for both present and future that he inscribe the paean.

Legendary and Quasi-Historical:

Visitor: Envoys of King Croesus of Lydia
Occasion: Croesus' projected war on the Persians
Question: Should I make war on the Persians? And with what army should I ally myself?
Response: If you make war on the Persians, you will destroy a great realm. Find the strongest Hellenes and ally yourself with them.
(Croesus made war, not realizing that the realm he would destroy would be his own).

Visitor: Heracles
Occasion and Question: Not stated
Response: You will die at the hand of a dead man, this is the end of your journeys.
(The oracle speaks of the centaur Nessus, who before he died from a poison arrow shot by Heracles, tricked Deianira into accidentally poisoning her husband Heracles some time later).