With the heart-piercer manticore wording reappearing in m19 I was wondering if there were still effects that required the throwing dagger wording.

Thanks.

Nothing requires the "if" or "when" wording per se. The question comes to whether or not you want to allow players to interact during the resolution of the effect. For example, in the case of Heart-Piercer Manticore, you don't choose targets for the ability until you decide whether or not to sacrifice a creature. It's two triggers hidden in one ability. In the case of Throwing Knife, the ability will kill Gossamer Phantasm even if you don't sacrifice the knife. In the case of the Heart-Piercer Manticore, you need to sac a creature of your own before you can target Gossamer Phantasm, so you need to be committed before you do things.

Same thing applies to "will they or won't they" situations? If your 2-toughness Gutless Ghoul is targeted by the Throwing Knife, then you have to choose whether or not to sacrifice Gutless Ghoul to its own ability before your opponent has to decide whether or not to sac the Throwing Knife, which means after you sac for the life, they can just not sac the knife, and if you don't sac for life, then they can kill you without you gaining life. In the same situation with Heart-Piercer Manticore, they have to sac a creature before you need to choose whether or not to sac the Gutless Ghoul to its own ability.

Wizards seems to have shifted gears and gone mostly with the intervening "when" wording on most cards, since it's a bit easier for newer players to understand and plan around, but in practise, there may come times where the intent of the card's abilities is such that an intervening-if clause will be more appropriate.

I don't want to sound pedantic, but "intervening if clause" refers to a specific phrasing that does not appear on Throwing Knife. "Intervening" in this context means "in the middle of a sentence." For example, Colossal Majesty has an intervening if clause, which means the if-condition is checked twice: once when it triggers to determine if it's put on the stack at all, and once again when it resolves to determine if the effect occurs.

Anyway, for abilities like Throwing Knife's that target, I expect them to use the new reflexive trigger template from now on. Brawl-Bash Ogre suggests they'll keep using the old template for cards that don't target, since it doesn't matter as much there.

Oh, thanks, mostly hoping that in most limited sets and in standard we won't have to care about the difference.