Hmm… I must say I like the OP of Angel Beats!. It’s piano-driven, with a heavy bassline, very catchy.
Ep. 02 starts with the Battlefront needing to replenish supplies and get new weapons from the Guild, where they make their weapons. It is latter revealed that they create things by ‘replicating’ it with their memories. Which is an awesome concept, especially if we can do that in the real world. ;_;