I don't buy much on impulse but if I do find something unexpected that I like and is reasonably priced I'll buy it. My grandson and I found a K-Line switcher at York a year ago with TMCC that was only $200 so we bought it. That's probably my largest impulse buy.
I need very little but every now and then there's an item that falls into that category, especially if it is holding up completion of something else. Right now I need Z-Stuff crossing gates for a spot in the back of the layout. It's holding us up from finishing the things closer to the front of the layout.
I want a lot of things - to convert our RMT Beep and a Williams GP-9 to TMCC for example. These are things I can plan and budget for. I recently did my first ever pre order - a TMCC gantry crane from Nassau Hobbies.