I've got a lot of picks today:
Start with a planeswalker:
Tamiyo, the Moon Sage
These aren't looking back. I don't think this is just a midstandardlifetime bump in this card, I think this is the start of this cards long-term popularity in modern and legacy (Avacyn block rotated out of standard when Dragon's Maze was released, which is when you can expect to see the lowest price on cards that remain popular for Extended, Modern, etc). I see these at $15 apiece within a couple months, $20 apiece by the end of the year.
This is such a powerful card. A silence and a counterspell rolled into the same converted mana cost as cancel. In the spirit of absorb and undermine, this is more powerful than both. I can see these up around $8.00 apiece as a staple in modern. Near-term performance depends on how popular UW becomes over the next season. If you can grab a few dozen of these around $0.75 apiece, I think it's an excellent investment, long-term and short-term.
Traumatize has been out of standard for a while. Mill decks have gained many powerful tools in last few years (including some planeswalkers). These were, once upon a time, worth $5.00 apiece. I can see them back up near $4.00-$5.00 if mill remains popular over the next year. I would pick up lots of these if you can find them around $1.25 apiece or less.
Master of Cruelties
Demands its own deck. In perpetuity (years from now), this will gain value. I'm guessing this jump is more of a correction and flattening out rather than a true on-the-up-and-up jump.
Prime Speaker Zegana
These are very powerful cards that just didn't catch on yet. Temple of mystery is climbing precipitously, so I think these are gaining steam. I wouldn't expect them to go much above $6.00 while in standard. You can see that the high-end retailers (CCG house, ABUgames, etc, are leading the price jump, not eBay and Amazon: this suggests that the jump will be minor (what you see above is probably as good as you can expect in the next few months).
Couple things to mention about this price graph. First of all, cards that are under a dollar typically sit at $1.00 apiece on eBay because of price minimums there. So often you'll see a card that starts around $0.25 or less and then, within a month or two, jumps to over $1.00 apiece. The price kind of snaps to $1.00 per card. Same is true for $1.50, $3.00, $4.00, $5.00 and $6.00, $10.00, $15.00, $20.00. This price-snapping phenomenon is important to keep in mind with all cards, but it's most important proportionally with low, quickly rising values.
I've wondered for years when this card would really catch on. It's a big flying body with two potent abilities. A training grounds vastly improves this card (W, B, U give you a killed creature or enchantment and the ability to do it again, it halves the activation cost). This is probably a quick, strong nudge upwards, I'd guess these will plateau around $6.00 apiece after this jump after rounding out around $8.00 apiece. Worth grabbing a playset right now. There's fewer than 50 cards left on TCGplayer, which is always an excellent bellweather for out-of-print card scarcity. I just bought a playset on eBay for $12.50 with free shipping, and I picked up a foil version off of TCGplayter for $5.50 total.
I got 4 at $0.75 apiece on tcgplayer. They're already close to $2.00 apiece in playsets on eBay.
from the looks of the above graph, one would think that these would plateau at $4.00 or so. Nope: on eBay these are already a solid $6.00 apiece, and playsets are putting them close to $8.00 apiece -- the loss of a just a few days' information is enough to change the analysis: this is, in reality, a double-jump - the graph above shows a single jump, another few weeks of data will likely show that this had two jumps within a few days of each other. TCGplayers has less than one page of items, and the change is price is pretty steep. I'm going to take a bit of a risk in buying 13 at $3.90 apiece. Worst case, I'll break about even. With a little luck, the $51.00 will become $120 in a month or so. See also Boon Reflection and Mana Reflection (both are jumping now, too, most notably Boon reflection - get foils of those before they're gone for good).
I've been waiting the these to jump for a couple years now. Supply (including the launch party promos) has finally been outstripped by demand. TCGplayer is running very low. I would not be suprised to see these plateau around $10 in a couple months. You can see from the coordination in Amazon and eBay prices, coupled with the nearly unchanged retailerer prices: this indicates that there is a baseline increase in price happening now, and no retailers are preparing for it by repricing, which likely means big corrections once they do start to move.
Skullclamp is finally scarce, after many years. I think you'll never see this card reprinted in a block, and it clearly has traction, so this is an excellent long-term investment. I'm considering getting about 8 at $2.25 apiece. TCGplayer is down to one screen (including foils) of original darksteel version. I'd bet than supply has never been so low. Plus, it's legal in commander now ( a case of a recent reprint causing nothing but a bump in value).
BUY BUY BUY!