I chose Garrus and Liara with my Solderr, with AP ammo as my Bonus power.
It was pretty good Garrus and I had Concussive shot, and Liara had warp to kill bariers, then Garrus and I had AP ammo to just own any armored targets. Not to mention Stasis, and Garrus being utter awesome with a Widow. --- They're a multinational corporation, not a pissed-off teenager-pauljc1 Official Shotgun Diplomat of the Mass Effect 3 boards.
I chose Tali and Garrus, mostly because of that final chat they had in the Normandy's battery room. Shepard recognized the fact they stuck with him longer than anybody else, so I couldn't bring myself to choose anybody else.
That said, they're also excellent for the final battle. Upgrade Tali's combat drone so it becomes a floating rocket launcher, and it can take out brutes before they ever reach you. Garrus' overload (with chain reaction upgrades), trip mines, and armor-piercing ammo are invaluable against defenders. You'll only have trouble with banshees (Tali's energy drain does help), but they're a pain no matter who you bring.