Su-Chi – Masters Edition rare. Su-Chi is a 4/4 for that provides four mana when it dies. Its name came from the word for "four" in two different languages.
Three Wishes – Visions rare. Three Wishes is unusual in that it explicitly allows its controller to look at face-down cards in the Exile zone. This used to come up when there was also a Mindslaver and a nonblack Wish, but now that the Wishes don't take cards from the Exile zone, it's harder to come up with an application for this rules quirk.
Two-Headed Giant of Foriys – Unlimited Edition rare. Early Magic card names had the occasional hidden pun. This is one that you might not notice unless you know that "Foriys" is supposed to be pronounced "Four-Eyes."
One With Nature – Scourge uncommon. One With Nature is one of those cards that encourages people to combine it with other cards and abilities. Double Strike! Landfall! And so on!
Time Vault – Unlimited Edition rare. Time Vault is one of those cards that has gone through a lot of different Oracle wordings. The current version goes back to the original wording, which allows for Twiddle shenanigans.
Mox Opal – Scars of Mirrodin mythic rare. In the real world, opals come in a wide variety of colors, including white, blue, black, red, and green. These variations in reflected color account for Mox Opal's ability to create any kind of mana.
Black Carriage – Homelands rare. On the discussion page for Black Carriage, ainsi_la_nuit says: "Thank you, Grand Creature Type Update, for allowing me to write that WOTC really put the carriage before the horse on this card." Nice work!
Red-Hot Hottie – Unhinged common. If you want to play a deck with real burn potential, combine Red-Hot Hottie with Obsidian Fireheart so you can spread blaze counters and third-degree-burn counters all over your opponents' creatures and land.
Bringer of the Green Dawn – Fifth Dawn rare. When we first saw Mirrodin (in Mirrodin), there were only four suns. It took the entire block's storyline to result in the green sun appearing in the sky!
Whitesun's Passage – Scars of Mirrodin common. "Whitesun" is a holy day for the Leonin of Mirrodin, when they celebrate the day when the white sun shines directly over Taj-Nar, beaming its light all the way down into the Cave of Light.
Carrion Call – Scars of Mirrodin uncommon. If you look closely at the art for Carrion Call, you'll see that the Phyrexian beetles are feeding off a dead wolf from Mirrodin. It might even be a Tel-Jilad Wolf!
Etched Champion – Scars of Mirrodin rare. It will come as no surprise that Etched Champion represents a descendant of Fifth Dawn's Etched Oracle. It helps that Matt Cavotta was able to reference his art from six years earlier!
Precursor Golem – Scars of Mirrodin rare. Mirrodin was created by Karn, the silver golem built by Urza. The plane was originally populated by golems that Karn created in his own image and left behind as he explored the Multiverse.
Memnite – Scars of Mirrodin uncommon. Memnite is the first pure 1/1 creature for in the history of Magic. Is it safe? Well, Ornithopter was a 0/2 flier for , and Dryad Arbor was a 1/1 that used up a land drop. So ... probably?
Platinum Emperion – Scars of Mirrodin mythic rare. From the Scars of Mirrodin FAQ: "Abilities that trigger whenever damage is dealt to you will still trigger because that damage is still dealt, even though your life total doesn't change as a result."