1.4 mostly, maybe 1.4.1 if you're unlucky... but both have been bypassed by every single cart worth it's money anyways.

Do you already have a cart, or are you looking?

 

It's most likely 1.4

A used one may come as 1.3 (like mine)

But yeah, as Rydian said, every single cart worth the money has a 1.4.1 bypass already anyway.

Just don't update your DS.

EDIT: Btw, ShadowSoldier, congrats on 1000 posts.

 

You're not going to find a new one with less than 1.4. 1.4 was pushed out around the beginning of the year.

When you buy your cart, buy it from a place that offers a flashing/update service (like shoptemp, this site's official partner store) and get that service when you order the cart, then they'll update it to bypass 1.4.1 so it's ready to use when you get it.

The Acekard 2i and DSTwo are two main recommendations.

 

Like I said, it's only up to 1.4.1, and any card worth it's salt works on 1.4.1 (after being updated).