Quick tip to any newcomers who are using T50 for rare-farming... if you see any quantum towers come out, click "Menu" and quit immediately. If you don't care about score, I find this saves a huge amount of time. Fighting those rainbows takes way too long and hardly ever yields a good card. I just won a Morning Star, three Druidic Staves, an Owl's Eye, two Fahrenheits, two Titans, an Eternity, two Pulverizers, a Trident, two Arctic Squids, two Miracles, a Discord, and a Lobotomizer in about three hours by skipping rainbows. 19 rare cards.
Already had a Vampire Stiletto, so the only weapon I'm missing is Arsenic. The only person in T50 I've seen so far with that weapon for farming is chaoz... and he stocks miracles too. He picked death mark and light towers, presumably just to annoy people, because with my full poison deck I managed to provoke five Miracles and get poison stacked over 50 before his Arsenic finally offed me. I'll have to stick a boneyard or two in there and try again.