The Binding of Isaac: Rebirth

Finally got a good Blue Baby run. I got the Blue Cross item from an angel room pretty much straight away.

Pretty early on I got the "Gnawed Leaf" item which makes you completely invincible if you stand still and don't attack. I thought "Pfft, what a useless item, when would I be standing still long enough?"
Cue amazed wonder when I got the Ludivico Technique and I realized I could just place it on a boss and then go invincible by standing still. I beat the entire chest by just standing still in every room and letting my tear and orbiting familiars do the work for me. Boring, but very very effective.

I did a similar thing against Mega Satan. Had Bandage Girl. Let her slaughter the hands and the summons. It was great. Made the whole fight easy. Then whenever there was a barrage of shots I just sat there until it all passed.

I'm a little surprised that they're already starting in on an expansion. It took over 2 years before Wrath of the Lamb came out, but then again their expectations probably weren't as high for the original as they are for Rebirth. I really like that they're accepting item ideas too; I wonder how many will actually make it into the game.

Ed also mentioned that a lot of the WotL and even original version difficulties were due to Flash. Something like 75% of compile attempts crashed the compiler in the late stages, and the ones that were successful were often corrupted instead. That's why the game just stopped updating and stopped changing. Flash was a huge limitation on the entire game that no longer exists.