There hasn't been anything said about Spartan Ops.
Well we did get the go ahead to say it because we (and pretty much everyone else there) experienced it in gameplay so here it is.
Promethean grenade. Spiked ball that when thrown turns into a power drainer that drains about 25% of shields over time. Its not very useful at all but it seems like it would be AMAZING for close range maps when trying to escape.
There is one more thing that I have not personally experienced so I wont say that one.