As of yet there is little known about items. We know that they will impact gameplay a lot, but here is the breakdown:

• Items can be bought around the battlefield at special stations
• The currency used will be called energy units
• Different mech types (light, medium, heavy) will be able to carry different items

There haven’t been any official announcements regarding specific items, but some things were mentioned in videos and interviews.
In the future, this page will contain a detailed list of items.

Hologram

Projects a hologram of yourself on the battlefield. If an enemy mistakes it for you and wastes his secondary weapon on the hologram, you might just have the advantage over him.

Tripwire

At this time, we can only speculate what exactly this is going to be. Maybe a tripwire rigged to explosive charges that you can deploy?

EMP

In the March 2012 Gameplay Teaser at about 0:39 you can spot a shockwave emerging from an enemy mech, disabling the players HUD forcing him to retreat. This could be an EMP-like device!