It seems that is has been discussed briefly before, but I want to clarify this once and for all. Many have claimed Buddha was Agnostic and some went so far as to say he was Theistic, with no scriptural evidence to back this up whatsoever. My position is that Buddha was Atheistic and in some cases, Anti-Theistic, but never Agnostic or Theist.
The Buddha's Direct Words from Scripture on the Subject of God
Buddha: "Others think that God is free creator of all things; clinging to these foolish notions, there is no awakening." [Lankavatara Sutra]
Buddha : "All such notions [of a] ...personal soul, Supreme Spirit, Sovereign God, Creator, are all figments of the imagination and manifestations of mind." [Lankavatara Sutra]
Buddha: This position rises the question of a first cause which the philosophers meet by asserting that their first cause, God and the primal elements, are un-born and un-annihilate; which position is without evidence and is irrational. [Lankavatara Sutra]
Buddha: "In this same class the disciples are the earnest disciples of other faiths, who clinging to the notions of such things as, the soul as an external entity, Supreme Atman, Personal God, seek a [belief] that is in harmony with them. ...But none of these, earnest though they be, have gained an insight into the truth of the twofold egolessness and are, therefore, of limited spiritual insights as regards deliverance and non-deliverance; for them there is no emancipation. They have great self-confidence but they can never gain a true knowledge of Nirvana." [Lankavatara Sutra]
Buddha: "The doctrine of the Tathagata-womb is disclosed in order to awaken philosophers from their clinging to the notion of a Divine Atman as transcendental personality, so that their minds that have become attached to the imaginary notion of "soul" as being something self-existent, may be quickly awakened to a state of perfect enlightenment." [Lankavatara Sutra]
Buddha: "Is it true that you hold that whatever a person experiences is all caused by a Supreme Being's act of creation? Then in that case, a person is a killer of living beings because of a Supreme Being's act of creation. A person is a thief, unchaste, a liar, a divisive speaker, a harsh speaker, an idle chatterer, greedy, malicious, a holder of wrong views because of a Supreme Being's act of creation. "When one falls back on creation by a Supreme Being as being essential, there is no desire [motivation], no effort [at the thought], 'This should be done. This shouldn't be done.' When one can't pin down as a truth or reality what should & shouldn't be done, one dwells bewildered & unprotected. One cannot righteously refer to oneself as a contemplative. This was my second righteous refutation of those priests & contemplatives who hold to such teachings, such views." [Tittha Sutta]
Buddha: "Others see the eternally of things in the conception of Nirvana as the absorption of the finite-soul in the supreme Atman; or who see all things as a manifestation of the vital-force of some Supreme Sprit to which all return; and some, who are especially silly, declare that there are two primary things, a primary substance and a primary soul, that react differently upon each other and thus produce all things from the transformations of qualities; some think that the world is born of action and interaction and that no other cause is necessary;" [Lankavatara Sutra]
Buddha's Discourse On God, the Absolute, the First Cause, and the Nature of Reality
From the Culla Vagga of the Tipitika:
"After taking his seat Anathapindika expressed a desire to hear a discourse on some religious subject.
"The Blessed Lord responding to his wishes raised the question, Who is it that shapes our lives? Is it God, a personal creator? If God be the maker, all living things should have silently to submit to their maker's power. They would be like vessels formed by the potter's hand. If the world had been made by God there should be no such thing as sorrow, or calamity, or sin; for both pure and impure deeds must come from him. If not, there would be another cause beside him, and he would not be the self-existent one. Thus, you see, the thought of God is overthrown.
"Again, it is said that the Absolute cannot be a cause. All things around us come from a cause as the plant comes from the seed; how can the Absolute be the cause of all things alike? If it pervades them, then certainly it does not make them.
"Again, it is said that the self is the maker. But if self is the maker, why did he not make things pleasing? The cases of sorrow and joy are real and objective. How can they have been made by self?
(Note: I think he is referring to a supreme spirit/soul [like a Holy Spirit I guess] because in English, "the self" refers to the Hindu notion of a soul [atman].)
"Again, if you adopt the argument, there is no maker, or fate in such as it is, and there is no causation, what use would there be in shaping our lives and adjusting means to an end?
"Therefore, we argue that all things that exist are not without a cause. However, neither God, nor the Absolute, nor the self, no causeless chance, is the maker, but our deeds produce results both good and evil.
"The whole world is under the law of causation, and the causes that act are not un-mental, for the gold of which the cup is made is gold throughout.
^^
(This is a very interesting point.)
"Let us, then, surrender the heresies of worshiping God and praying to him; let us not lose ourselves in vain speculations of profitless subtleties; let us surrender self and all selfishness, and as all things are fixed by causation, let us practice good so that good may result from our actions."
[Culla Vagga 6:2]
(Note: For those who think the word "God" wasn't in his vocabulary, the Sanskrit/Pali words for God are "Ishvara" and "Brahma" referring to God/Supreme Being/Lord/Creator/First cause, etc.)