Intuition is a good advanced trait if you know how to use it properly, i for example just seem to play bad when i know where the baddies are hiding ;-)
Wizzkid while being good is luck dependant, without Mods, Whizkid levels are useless.
Badass, especially if a marine is awesome.
But my all favorite advanced trait is JUGGLER. That thing is owerpowered, and allows for crazy combos, instant switch to whatever weapon is best at a given moment.
Currently what really is unbalanced is ammo, there is a crazy hell lot of it all over the place... Might as well remove the need for ammo alltogether.