I've been to Berlin for a few days, and to Amsterdam twice.
Berlin:
-Get some street waffles. I'm not kidding, they're amazing.
-Checkpoint Charlie is kinda a must. You can see bits of the wall all over though. A lot of the slabs have been re-purposed as street art.
-If you're single (or pretending to be), you could check out an FKK club. Basically, from my understanding these are like a super brothel, stocked with 10s, who will sell themselves to you for a half hour at a time for something like $60 euros. I've never been, but a friend of mine has and he never shuts up about how awesome it was. They're legal there.
-The casino (I think there is only one) is kinda a fun experience. You'll need to wear a suit. Also, its been a few years, but I'm near certain the Roulette wheels don't have 00 on it. So, if you ever wanted to play roulette, this should be where you do it.
Amsterdam:
-Despite being there twice, I didn't smoke pot, get a hooker, or see a live sex show. I only regret passing up on the third one. Sounds memorable.
-Red light district window shopping is kinda depressing.
-Heineken Brewery tour should be mandatory. Not sure what it costs now, but when I went it was 2 Guilders (which was dirt cheap). They get you bombed.
-International Sex Museum isn't as cool as it sounds.
-The streets and canals at night are just beautiful. Walk this city or bike it if you can. Sunset will be LATE.