Has anyone ever seen God and, if so, what does he look like?

No one has ever seen God (John 1:18, 1 John 4:12). God is invisible to us (Colossians 1:15, 1 Timothy 1:17). He lives in unapproachable light where he cannot be seen (1 Timothy 6:16). No one is holy enough to see him (3 John 1:11). However, he does not necessarily hide himself completely from us. There are several individuals throughout the Bible to whom God has shown himself to in various, tangible forms (theophany - visible appearance of God to man) -- whether showing his back side, veiling his glory in a cloud or a pillar of fire, appearing in the form of an angel, the likeness of a man, or Jesus incarnate. This is to say that mortal man has never seen God in his true form, only a comprehensible likeness (Numbers 12:8), and we were made in his likeness (Genesis 1:26). One day, however, all inhabitants of the earth will see God's face (Revelation 22:4).

        Oh, that you would rend the heavens and come down, that the mountains would tremble before you! As when fire sets twigs ablaze and causes water to boil, come down to make your name known to your enemies and cause the nations to quake before you. Since ancient times no one has heard, no ear has perceived, no eye has seen any God besides you, who acts on behalf of those who wait for him. (Isaiah 64:1-4)

      The following individuals have seen the likeness of the Lord in one form or another. In many cases where the person didn't know who it was at first, God refused to tell them his name because it was either too wonderful or beyond their comprehension.

      Adam and Eve, it may be inferred, saw God in the Garden of Eden on a regular basis. After eating of the forbidden fruit of the tree of the knowledge of good and evil, God was walking through the garden in the cool of the day and Adam and Eve hid from him (Genesis 3:8-10).

      Hagar, Abraham's mistress, saw an angel of the Lord when she fled from the abuse of Abraham's wife, Sarai. The angel told Hagar that she would give birth to Abraham's first son, Ishmael. According to Genesis 16:13, "She gave this name to the LORD who spoke to her: 'You are the God who sees me,' for she said, 'I have now seen the One who sees me.' "

      Jacob, the second son of Isaac, wrestled one night with a man who wrenched his hip socket out of place. At daybreak the man went to leave and Jacob demanded of him his blessings, to which the man replied, "Your name will no longer be Jacob, but Israel, because you have struggled with God and with men and have overcome," but he refused to say his own name. Jacob named the place Peniel, meaning "face of God," because as he said, "I saw God face to face, and yet my life was spared" (Genesis 32:22-32).

      The seventy elders of Israel, along with Moses, Aaron, Nadab, and Abihu saw God on Mt. Sinai after leaving Egypt, just before the issuing of the ten commandments (Exodus 24:9-11). God had invited these individuals to come up and worship at a distance (Exodus 24:1-2), although when the time came they were allowed to eat and drink in his presence.

        Moses and Aaron, Nadab and Abihu, and the seventy elders of Israel went up and saw the God of Israel. Under his feet was something like a pavement made of sapphire, clear as the sky itself. But God did not raise his hand against these leaders of the Israelites; they saw God, and they ate and drank. (Exodus 24:9-11)

      Moses, the servant with whom God was pleased, was granted his wish to see the Lord's glory, however, God warned him that he could not see his face, for God said, "no one may see me and live" (Exodus 33:17-23). So God covered Moses with his hand until he had passed by and then removed his hand so Moses could see his back. He also said his name, the LORD, as he passed.

        And the LORD said to Moses, "I will cause all my goodness to pass in front of you, and I will proclaim my name, the LORD, in your presence. I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion. But," he said, "you cannot see my face, for no one may see me and live."
        Then the LORD said, "There is a place near me where you may stand on a rock. When my glory passes by, I will put you in a cleft in the rock and cover you with my hand until I have passed by. Then I will remove my hand and you will see my back; but my face must not be seen."
(Exodus 33:19-32)

      The Israelites, during their exodus from Egypt to the promised land of Canaan, were led by the Lord, who veiled himself in a cloud by day and a pillar of fire by night (Numbers 14:14). They also saw the "glory of the LORD" atop Mt. Sinai while Moses was with him (Exodus 24:15-18), which looked like a consuming fire.

      Gideon, one of the early judges of Israel, may not have actually seen the Lord himself, but an angel. Still, he thought that since he had seen the angel of the Lord face to face that he would surely die, but God comforted him (Judges 6:17-24).

      Manoah and his wife, the parents of Samson, were visited by the angel of the LORD who told them of the birth of their son, even though she was sterile. The angel refused to say his own name. Manoah and his wife offered burnt offerings on the altar to the Lord and the angel ascended in the flame, to which Manoah exclaimed, "We are doomed to die! We have seen God!" (Judges 13)

      Job, the righteous man of God who was tested by Satan, after he had argued with his friends about the reasons for God's afflictions, was visited by the Lord, who spoke to him out of a storm (Job 38:1). Afterwards, Job said, "My ears had heard of you but now my eyes have seen you." (Job 42:5)

      Elijah the prophet went into the Lord's presence on Mount Horeb. The Lord passed by him with a gentle whisper after tearing apart the mountain with a mighty wind, an earthquake, and fire. Elijah had to cover his face before coming into the Lord's presence (1 Kings 19:9-14).

      Isaiah, when he was officially commissioned by God to be a prophet to Israel, saw the Lord in a vision (Isaiah 6). In this vision he saw the Lord, seated upon his throne in glory and surrounded by seraphs.

        In the year that King Uzziah died, I saw the Lord seated on a throne, high and exalted, and the train of his robe filled the temple. Above him were seraphs, each with six wings: With two wings they covered their faces, with two they covered their feet, and with two they were flying. And they were calling to one another:
        "Holy, holy, holy is the LORD Almighty; the whole earth is full of his glory."
        At the sound of their voices the doorposts and thresholds shook and the temple was filled with smoke. "Woe to me!" I cried. "I am ruined! For I am a man of unclean lips, and I live among a people of unclean lips, and my eyes have seen the King, the LORD Almighty."
        Then one of the seraphs flew to me with a live coal in his hand, which he had taken with tongs from the altar. With it he touched my mouth and said, "See, this has touched your lips; your guilt is taken away and your sin atoned for."
        Then I heard the voice of the Lord saying, "Whom shall I send? And who will go for us?" And I said, "Here I am. Send me!"
(Isaiah 6:1-8)

      Ezekiel, when called to be a prophet while in exile in Babylon, saw a vision of the heavens opening and the Lord appearing as the likeness of a man seated upon the throne (Ezekiel 1), along with four winged creatures riding atop wheels out of a lightning storm, which were later identified as cherubim (Ezekiel 10:15, 10:20). The likeness of the figure on the throne was that of glowing metal from the waist up and fire from the waist down, and he was surrounded with a brilliant light -- and it was this figure that "was the appearance of the likeness of the glory of the LORD" (Ezekiel 1:28). It was this figure that also appeared to Ezekiel on other occassions, such as when he was taken to the temple in Jerusalem in a vision of God (Ezekiel 8:2-3) and shown the idolatry that the Israelites were participating in both openly and in the secret chambers (Ezekiel 8-10).

        Spread out above the heads of the living creatures was what looked like an expanse, sparkling like ice, and awesome... Then there came a voice from above the expanse over their heads as they stood with lowered wings. Above the expanse over their heads was what looked like a throne of sapphire, and high above on the throne was a figure like that of a man. I saw that what appeared to be from his waist up he looked like glowing metal, as if full of fire, and that from there down he looked like fire; and brilliant light surrounded him. Like the appearance of a rainbow in the clouds on a rainy day, so was the radiance around him. This was the appearance of the likeness of the glory of the LORD. (Ezekiel 1:22-28)

      John, brother of James and son of Zebedee, one of Jesus' apostles, saw God in a vision while in the Spirit during his exile on the island of Patmos. The image was described much like the ones seen by Isaiah and Ezekiel. It is also revealed later in his vision that God will one day dwell with men on earth and they will see his face (Revelation 21:3, 22:4).

        At once I was in the Spirit, and there before me was a throne in heaven with someone sitting on it. And the one who sat there had the appearance of jasper and carnelian. A rainbow, resembling an emerald, encircled the throne... From the throne came flashes of lightning, rumblings and peals of thunder... Also before the throne there was what looked like a sea of glass, clear as crystal. In the center, around the throne, were four living creatures, and they were covered with eyes, in front and in back. (Revelation 4:2-6)

      The Apostles, along with all of Jesus' disciples and anyone else who ever laid eyes on Jesus while he was on the earth have seen God. Jesus plainly told his disciples that anyone who has seen him has seen the Father (John 14:6-11). In John 12:45, he is recorded as saying, "When he looks at me, he sees the one who sent me." Colossians 1:15 says that "he is the image of the invisible God" and Hebrews 1:3 says that "the Son is the radiance of God's glory and the exact representation of his being."

        "If you really knew me, you would know my Father as well. From now on, you do know him and have seen him."
        Philip said, "Lord, show us the Father and that will be enough for us."
        Jesus answered: "Don't you know me, Philip, even after I have been among you such a long time? Anyone who has seen me has seen the Father. How can you say, 'Show us the Father'? Don't you believe that I am in the Father, and that the Father is in me? The words I say to you are not just my own. Rather, it is the Father, living in me, who is doing his work."
(John 14:7-10)