checked the comments to see if anyone else had any problems and saw everyone suggest frag bombs. I tried em, at first they seemed "pretty good". But once I upgraded them about 3-4 times I saw just how ridiculously ultra-powerful these things really are... frag bombs, the REAL ultimate weapon of this game.
I bought laser first because at first glance, its speed VS damage looked promising. It went great at the beginning. I kept upgrading it and got a bit disappointed later on. At one point it became so frustrating trying to take down those white space shuttle things I just started ramming into them out of rage, too bad that does not give me any money... So then I said F it and bought the H bomb. Needless to say I went straight back to laser, and after a few levels of monitor-punching I
For the destroy Neko's Shop achievement you have to face it as a "boss" in boss world. Just purchase the boss world pass in the black market after you get the legendary key and it should appear as an option when you click leave shop.
 "Seven Deadly Sins"){kind=icon}
 "Notebook Wars"){kind=icon}
 "Enigmata 2: Genu's Revenge"){kind=icon}
 "Epic Combo!"){kind=icon}