Several strong picks today.
This faerie staple saw a 2013 Modern Masters reprint (originally Eventide). Notice the hard-line once it hit $5.00 - this is due to speculators and stores deciding/knowing that this card will see a rebound (it was like $15.00 and rising before the reprint). In this case, it's a sign of health, and clearly the bottom. That was your time to buy. However, the slope now is strong enough that a spike seems upcoming. Notice how the price snapped to $8.00 for only a few weeks - it could not hold it. $9.00 will be even shorter, as the slope is increasing and it's closer to the natural price point of $10. Once it hits $10, it will feel pressure to go to $12, but likely it will quickly decided to jump to $15.00, all by (my guess) April 2016.
Subtle, simple power. If you can find these under $1.00, buy. One reprint in the bag, and the climb continues unabated and now with partial immunity to reprints). The Duel deck reprint was in May 2014 (you can see it in the graph). When a card eats right through it's first-reprint decline in about a year, you know it has legs.
Staple that just won't stay down, reprint after reprint. Another reprint would hardly shake this card, and I can see it reprinted as Uncommon no problem. Buy if you can find at $1.00 or less.
Eldrazi hype, casual appeal, and ever-evolving token strategies make this a hot item right now. Anything under $3.00 looks like a good investment. Also has 2 reprints under it's belt. I highly doubt this will see a reprint in the BFZ block.
Must be for Commander. Weird old powerful card with goofy art, must be just powerful enough that no one much noticed before now. Can bring the game to a halt, except for players playing black, and can be grabbed on turn 2 with a dark ritual. These are great to trade for, or look for in $1.00 bins. Might find a Commander reprint in a year or two, but it would probably only cause price to stablize and legitimize - Commander reprints can introduce huge newer audiences to old powerful, rare cards that have been overlooked for years.
Bonus pick: Khans of Tarkir Booster Boxes (fetch lands are eternal). The expected median value of opening a box is steadily climbing over $110 - this is very impressive considering the vast majority of the value in the set is the fetch lands, which, unlike the reprinted shocks, look healthy to keep gaining for some time. Many other big cards in the set are on the upswing after falling from their release highs. I can see a box of Khans going for $300 apiece come April 2017 (for reference, Zendikar boxes, released almost 6 years ago, are over $500 apiece now, largely due to the OTHER fetches - though they were NOT reprints). I hope to grab an armful for in-print prices. They are either out-of-print now or will soon be.