I've always assumed the Haitian was the one who blocked other Heroes' abilities. However, when Sylar is captured, HRG says: "Everyone else we've encountered has only one ability. You appear to have several" (or words to that effect). Assuming the mind-wipe is one of the Haitian's abilities, we have several options:
1) HRG was lying
2) The Haitian has a single, general ability that somehow encompasses both power-blocking and mind-wiping
3) HRG is a Hero, with the ability to block powers
4) HRG has access to a device that blocks powers
I don't think it likely that HRG was lying. He didn't need to tell Sylar that they'd never met anyone else with only one ability, and it felt more like he was trying to confide in Sylar as a way to get him to open up.
If someone can think of a plausible, general ability for the Haitian to have that can encompass both powers, shoot. Someone on another thread suggested that the Haitian could erase thoughts as they happened, thus preventing anyone from using a power that had to be consciously triggered. However, if he had that ability, he'd also have the ability to pretty much stop anyone in their tracks - he could erase their thoughts of moving their legs or arms, lock someone into stasis. He hasn't shown any sign of doing that, and I think that's a bit of a stretch.
I don't like the thought of HRG as a Hero - I think he has more impact as a normal competing as an equal in a world of Heroes.
The technological measure sounds more likely to me, as it would also explain how they power-proofed Sylar's enclosure, and how he managed to use his powers anyway (Eden disabled it when she entered).
It could also be a combination of the last two: HRG has the power, and through experimentation was able to create a device to replicate the effect.
Thoughts?
