Diremongoose
iSpy
Whether you prefer rifles or pistols, keep a rifle with jump shot handy when you're doing jump puzzles. The Engi can use jump shot to guarantee a successful vertical jump. Unlike other skills that move you around, you choose the exact point of exit from the jump. I've managed to cut out over a third of the jumps in the WvW jump challenges (though I had to know where I was going first!)