Here's my 2 cents (adjusted for inflation, it's worth less than zero).
First, decide on the "look" you want. By that I mean, are you a Star Wars fan, Star Trek, LOTR, Batman etc. Figure out a "sphere of influence" for the item.
Then decide how deep, or subtle, you want to go. Do you want it to SCREAM Star Trek (for example), or be more subtle, so that those "in the now" would know, and others would overlook it.
Once those two details are sorted, gather images (even if totally unrelated) to use as guidance/influence.
A sketch, if that's your thing (personally, I'm not good a sketches, so I just build)
Finally, start the build, keeping in mind it must be functional, so height/length are critical to function, and safety too (make sure the tip is not slippery for example). Consider the angle/curve/shape of the grip. This is full custom, so it should be tailored to your exact needs. If you are a woodworker, splurge on some cocobolo, Indian rosewood (Brazilian is banned these days) bloodwood, purple heart etc. You can easily do pearl inlays- pre-cut dots are available from Stu-Mac (and other luthier suppliers); drill a flat hole with an end mil or a forestner bit, and glue them in. Sand flush and clear. Combinations of the above are nice too. Older pool cues used linen cord for the wrap. The original "Cortland" linen is hard to find now, but plenty of other options. Avoid nylon cord. It is slippery, hot and hard. Not comfortable. Maybe integrate a small LED light in the handle, to assist with dark keyholes...
Some ideas: Perhaps consider leather wrapped closed-cell foam for the grip. Maybe a BMX bike grip- a rainbow of colors (and some not appearing in the rainbow as well) used as-is, or modified. If you are adding "greeblies" to it, consider a carbon fiber tube as the "core" to reduce weight without losing strength. It's hard to cut (dulls just about everything) but super-strong, and available cheap on eBay and elsewhere. Some places offer cutting service if you know the length. To that end, rather than one tube, perhaps a bundle of smaller tubes would create the look you want. Mix copper tubing with the carbon tubing for a unique look. Maybe stainless tubing or even soft PVC tubing (hose), which comes in all sorts of colors, just like wire and cable.
This could be a really fun project!
