Tag / Fallout 3
There was only one quest related mission that I needed to finish in the base game, but it would require collecting 30 bottles. I decided to head off and start collecting the Bobbleheads that I had missed. Luckily there were only two potentially missable ones that I hadn't screwed up storyline wise so I grabbed them first. I continued to wander the wasteland for another hour or so locating another 6 before I had grabbed half of the collection. Along the way I was able to net a few Quantum Cola bottles, so I should only need to collect another 10 more. Fawkes and I were also able to reduce the kills needed for the 300 humans killed achievement by about 30 through random encounters while Bobblehead hunting.
After a lengthy stint away from the wasteland I decided to head back in and clean up the remaining achievements while I waited for the new Mass Effect game to be released. I was pleasantly surprised to find that I only had four quest based achievements lend in the base game (none of which could be missed due to the outcome of other quests).