Counters

[He-Man]

You mean like trap cards? That's the only reasonable way this would work.

We DO have trap cards. Hunters' death and web traps.
I do think we need more though...

Exactamundo. There are too little traps now, so there is hardly any surprise element.
As mentioned above, they should be low cost to be effective, or have a more detrimental effect.
Anyway, without being able to actively intervene on your opponent's turn, these triggered effects are the only way to get something remotely close to a counterspell. Other "traps" could have things like "next time one of your allies is attacked, that allies gets +2 power and +2 health" or something.

[Scion]

It is a great mechanic. In yugioh you had traps that would negate the next "ability" card that your opponent played, kill the next summoned creature, give extra attacking power to your creature etc

[Reshiram99]

+1 to instants.

[MattOG]

Shameless Plug

First 5 or so are traps

[Gondorian]

Shameless Plug

First 5 or so are traps

I really like Counter Attack.

[Hotwarriorchick]

hey boys xx, check out my post. MUAH

[Ailaik]

Wow, a lot more reactions than I expected. More different traps would be a cool alternative indeed.

[nrjenbar]

+1 for traps
and the cost of traps should be the same for all... or should not appear in the resource display (but paid)

A hunter playing a trap : you know the trap he played simply in looking the cost in resource paid for the card.
Webbed or Killed...