I'm nearing the end of Borderlands 2, and there are some side quests ranked trivial that I would rather not bother with. I have some of the SDUs from the black market, but not all of them.
I'm not concerned with missing out on some level 20-25 unique blue or purple stuff; I am concerned about starting a second playthrough and being cut off from some SDUs or otherwise unattainable upgrades, permanently. Can this happen? Are there any permanent upgrades that occur once per playthrough and are not available from the black market?
Best Answer
No, the black market tracks your progress between all playthroughs, and all other upgrades (ie, additional weapon slots) are unmissable/plot related.
If you pass up on these side quests, you may miss out on achievements, some (probably pretty poor) loot, and other quest rewards like Eridium, XP, or cash. However, you won't miss out on anything permanently, nor anything essential.
Do note that starting playthrough 2 means you won't have access to Sanctuary until you advance the plot to that point (probably an hour or two of play). However, at any point you can return to your first playthrough to return to Sanctuary and/or complete any of these quests you may have passed up on.