The DEMP was amazing in Nar Shaddaa or other maps with a lot of ledges, but that's about it. I think in JA they removed the shockwave that it created? That made it virtually useless.
The lightsaber was fairly useless in MP, but more useful in SP. I remember it being more useful than it was in JK, because in JK you couldn't deflect blaster bolts well while running forward.
Oh and yeah, the Bryar was amazing. Bryar snipes from across the map were very satisfying and very humiliating to the enemy.
Also, TDs in any JK game weren't useless, but not as effective as they should have been. In the SW universe, TDs vaporize just about anything within their blast radius. Personal shields help, I guess, but if you're low or out, one TD should kill you instantly.
I remember the UMP 40 and 45 being very effective for close to medium range in the Rainbow Six games. 45 stopping power in full auto, you don't wanna be on the other side of that.
Bassoon, n. A brazen instrument into which a fool blows out his brains.