Case in point: pick adze tip guard for an ice axe. There are several on the market for $5 to $15, clever Grivel even incorporates a spike guard into its leash. In a pinch, you can fashion one out of a scrap of leather and some duct tape as Dancesatmoonrise describes, as well as an UL leash. Thought I'd try making one at of materials I already had on hand, as most DIYers have various (s)crap on hand.

Here's the first I made. The I.D. of the vinyl tubing was 1-1/4" for the adze, think 1/2" or 5/8" for the pick, and 1" for the spike. There are two holes each for the adze and pick covers. The 1" I.D. is a perfect fit on this shaft and almost doesn't need a stop. A key ring works great for this. If you cut some grooves and used the lower rivet hole to put a stop through, 1" I.D. could also make a nice non-metal grip. Made a second one. Again, 1" I.D. with a key ring worked great on the shaft, and the angle makes it a little easier to slide on. If stuck when removing, give it a twist. Adze and pick covers have a single hole and I tried using the iron to weld the end closed for the pick, though it made more of a mess. Regardless, the 3/4" I.D. still jams before the pick tip comes close, Grivel's being bigger than BD's. Slip Fit versus Stretch Fit: Haven't tested them by tossing them in the freezer, but rubber or vinyl aren't as pliable when cold, so there's a chance a stretch fit could be stuck hours into a winter hike. Leave it outside the night before to test. If too snug, simply remove it before you leave your car. Guards are mainly for storage and transport any how.
Sizing Tip: Not sure which I.D. to use on your axe? If you can't take your axe into the hardware store, wrap a strip of paper around the widest part and mark with a pencil where the start to overlap to find the circumference. Measure in inches and divide by 3.14159 to find the minimum, though you'll likely go up to the next size as stretched tubing wants to return to round and thus will "grip" smaller flat circumferences. The BD adze was wider than the Grivel and I had to stretch using a couple long, parallel screwdrivers and light torch heat -- DON'T inhale any vinyl fumes nor rubber.

Lastly

Who else has DIYed some gear stuff? Photos?