Reflective safety tape makes great lightweight reflectors, comes in a variety of colors, and looks like accent paint in sunlight.
The best penetrants I've used come from when I was a boat mechanic: Zep 45 and Zep PLS (which can also be used as a metal protectant to some extent). Not the cheapest, but the cans last forever as the propellent is perfectly matched to the amount of material in the can.
For bar wrap, I use two methods to secure the end:
1. For a cleaner look, I wrap towards the bar end, overlapping the start of the tape so the starting side is secure and then the bar end plug can be used to secure the loose end when finished.
2. For a more vintage look, I wrap from the bar end and use cloth string (white can be dyed any color) to secure the loose end in the center of the bar. There are plenty of methods for wrapping and tying off the string cleanly that can be googled.
I've also used cloth tape to wrap over rubber grips that are comfortable, but don't otherwise match the look of the rest of the bike.