Can you use the marcus quests in sanctuary that allow you to kill the vandal etc to complete challenges?
For example, right now I’m trying to complete the shotgun challenge to kill enemies at point blank range and it’s a pain. Can I just use the glitch to go in there and massacre them to complete the challenge?
The “vandal” side quest? Not sure what you mean there. For the shotgun & sniper challenges, I’ve just done Pete’s bar, or run around any area where there are generally large mobs. If you didn’t do any of the arena side quests (Fridge, Creature, etc.) in an earlier play-through, you could go back and do those.
I think he’s talking about the mission at the beginning of the story where you test elemental weapons at the shooting range behind Marcus’ shop. I don’t remember if the target “dummy” counts as a kill during the mission, but I don’t think it does. My advice would be the same @VaultHunter101 gave you. If you have the Torgue DLC, switch back to normal mode (assuming you’ve already completed your first playthrough), go to Pyro Pete’s bar, equip a Jakobs shotgun, run up to enemies and just shoot everyone in the face. You’ll have the challenge completed in no time and you’ll also get a whole bunch of torgue tokens in the process. If you don’t have the DLC, just do the same in any of the circle of slaughter arenas. You just need small areas that are loaded with enemies to complete those challenges.
I completed the “Open Wide” challenge quite easly in the Caustic Caverns, on Normal Mode.
There are hundred of Varkids and Spiderants there, just run around and shoot at your feets, by the time you clean the map the first mobs you killed usually already have respawned.
Took me less than one hour to get the two last ranks of the challenge.