The vast majority of onsite interviews I've had were exhausting Google style interviews. Generally speaking, the ones that haven't been were the ones where I got the job (exception is the current job, that was a two hour sit down exam where I was left alone. I made it, but I'm surprised I did. I've seen dozens of people come in and fail at the test since).
My favorite interview, in fact, was one were a grizzled veteran (he was the Lead Programmer on NBA Jam), asked me a couple questions on the code sample I brought in, showed me an example (uncommented) class from their actual code base (I verified later) and asked me to interpret what it's doing, asked me a couple more questions, then said "Okay, I know you can handle the job, now let's see what you really know."
And he proceeded to ask me deep questions about memory and graphics, which I could only partially answer most of them, and then he proceeded to teach me about the details.
It felt more like a mini-lecture at that point than a pop quiz ("Do you know this? No? Well tough! Better look it up later. Next question!"). I legitimately learned things from that interview that I can still recall today.
Then I had a friendly chat with the president of the company afterwards, who used to work for Midway and designed many classic arcade games, most notably Rampage, about what they do at the company. I played that game a ton when I was a kid, so I was happy just to be chatting to him like we happened to run into each other at a family BBQ.
I was in and out of there in about an hour, and there wasn't even a weed-out phone screen.
Then I got a job offer a few days later, which I ended up accepting.
