I think The Pitt DLC has something like this. You fight 3 times, each time getting a little harder (a cake walk at lvl30). Point Lookout DLC also has a Safari thing, where waves of ghouls charge you and you have to kill a certain amount. The PL one is repeatable (1K caps a pop), which is pretty cool (at 30 it's ridiculously easy though).
In my efforts to think of some fun repeatable stuff to do, an arena type thing came to mind. though, it's more than I can bite off at the moment - and foreseeable future
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Please excuse my horrible paintshop skills, but http://img15.imageshack.us/img15/3568/arenat.jpg. The fight pit is fenced off. NPC's spawn in the pink area and the player or NPC's spawn in the turquoise area (player talks to cashier, enters self, walks down left side to enter pit). A few NPC's cheering on the fights in the spectators area.
The player would be able to bet on fights between NPC's/creatures or they could enter themselves as a fighter. The NPC's and creatures would be divided up into classes: Lightweight (Rad Roaches, Mole Rats, etc), Middleweight (Humans, Ghouls, etc.), Heavyweight (Super Mutants, etc.), Super-Heavyweight (Behemoth). If it's a heavyweight vs a middleweight, there would be 1 heavy and multiple middles, etc (preferably all lvl with player).
The Betting / Cashier would be a computer like you know who (maybe a scoreboard above it), but have dialogue like: Would you like to place a bet (current fight), Collect your winnings, Setup a fight between two classes (ability to enter yourself), etc. Because it's a computer, the voice files can be made using text-to-speech.
Maybe something like win ten in a row for the title (bigger payouts or something). Dunno if the NPC's can still keep fighting on a schedule if the player isn't there, or just fake it with a random so that they could win the title back.
I think that would be a lot of fun
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