You can easily kill yourself with a water overdose (and it's actually fairly common),so yes.
Nutmeg was already mentioned - high doses can easily kill someone, sadly even without hallucinations simply by killing off ones liver and dying an agonizing death a few days later. The same goes for cinnamon, but with a much lower dose.
There are a few more, but I don't want to give people too many ideas.
To make it short: Yes, possible,but it's mostly a very slow death over multiple days that fucks you up really bad and is a horrible way to go.
You are really surprised by a guy who wanted to name his car series S-E-X-Y and had a temper tantrum when model E was taken and he could not "buy" it.