In terms of more expensive cards, the first thing that comes to mind are dual lands. The
shock lands (
Temple Garden, in these colors) are great, since you get to decide if you need that mana NOW and pay the two life, or if you're sitting pretty and can handle the delay. My other favorites are the filter lands (
Wooded Bastion) which can color fix you to two off color mana instantly. It also bears mentioning the bounce lands (
Selesnya Sanctuary) which essentially count as two seperate lands in one card (i.e. you start with this and two
plains, if you don't pull any other lands, you'll still have access to 4 mana) and the M10/Innistrad tap lands (
Sunpetal Grove) which will be straight up dual-color-no-drawback lands as long as you draw any thing else as well (combos with the
shock lands just fine)
Another card that I didn't mention ealier due to cost is everyones current favorite flickerer,
Restoration Angel. She's got
flash, so she drops in as a suprise blocker with flying and 4 toughness, which is great by itself, but she'll
rescue a dying creature, or trigger someones ETB at the same time. Expensive but worth it.
Also, most people are comboing
Restoration Angel with the green
Thragtusk right now. Notice how its effect is "when
Thragtusk leaves the battlefield" not when he dies, so a
flicker on that beast gets you a 3/3 AND 5 life. He might come down in price after he rotates out when M14 is released, but I doubt it will be very sudden.
If you were in Red, I'd suggest
Thundermaw Hellkite. In fact, I'll even suggest splashing red FOR
Thundermaw Hellkite. When he enters the battlefield he taps all of your opponents' flying blockers, and attacks for a hasty 5.
Flicker him each turn before combat and the game's over in another 3 turns! Use those dual lands we talked about earlier!
Got plenty of mana you say?
Tooth and Nail is your solution. Just read it and realize all the win, especially if Thundermaw and
Thragtusk are in your library. Even without, you can tailor your picks to the ETB effects that will put you in the best position.