The Squirt Pen! This one is on the cheap side, lacking a ballpoint and having a really terrible squirting mechanism, but I've had better versions that could've fooled just about anyone. Still, holding the pen in the necessary position to squirt someone is a pretty obvious tip-off even if it looks real. Can't say that this edition is too genuine, unless the pen sizes I've encountered are more of a local thing while the rest of you scribble in your diaries with magic marker-wide pens.
Oh, and do you see that little ditty on the package, detailing how the pen can squirt water up to thirty feet? MY ASS. I could barely get it to dribble, and when it would, it dribbled on me. I haven't been that disappointed since the Sunshine Company stopped putting those side panels on Cheez-It boxes that suggested the crackers were perfect crumbled salad toppers. I miss that side panel so much.