If you could alert your receptionist not to put it in the slush pile, that would be good!
1. Hand-delivery. Most agents hate it.
2. Assuming you're allowed to stop by--and not asking. Would you stop by a doctor's office without an appointment? No. And you pay doctors for their time. We don't get paid per meeting. So, even less polite.
3. Assuming we have a receptionist, or someone who just sits there waiting for visitors. No. Giant, corporate agencies have them. Boutique agencies do not. When we have guests, they're invited, and we take care of them ourselves. Which I like. Who doesn't like having a literary friend over for tea (and sometimes cheese and fruit and chocolate)? I mean, really. I wouldn't outsource that to anyone. :)
4. Assuming that because you ask, you'll get special treatment.
One thing that should be clarified: a lot of authors get rather prickly when we mention "slush." To us, slush simply means all incoming manuscripts that are not connected to people we know personally. I guess the slushiest slush is unsolicited.
Once an author (who was not someone we knew personally--we eventually took her on, though) got really mad because, she said, she "accidentally ended up in the slush and [Gatekeeper] had to fish her out again." No. Not a mistake. You are automatically slush. This doesn't mean that you're auto-rejected if we dislike your font. It just means that you have to get in line with everyone else, and you have just as good a chance as anyone. It's all about your writing, in this case, and not your connections. Which, really, is just fine. Contrary to popular opinion, we won't give a huge edge to people just because we know them. It doesn't matter if you're our best friend of ten years. Will an editor buy a book just because I add to the pitch, "and this writer is my BFF, like, OMG forever, I love her"? No. I saw a comment in Poets & Writers once where a writer wrote in saying that the only reason she was rejected was because she didn't have a personal connection to an agent--and that this was the only way to get published.
Whew. As you can see, Gatekeeper's crashing from party-planning caffeine high to it's-almost-lunch grumbly.