I absolutely LOVE PVC pipe. (no not that way).
I use 3" pipe cut to length for my dumbells, instant thick grip dumbells. Cut them long so they are jammed against the plates, and use screw lock dumbells. You can even force the handle to be "off centre" this way.
Or cut them a bit shorter, and you got a rotating dumbell. Stick them on a really heavy dumbell and you got something like the "rolling thunder" that ironmind sell. Bloody great for one arm deadlift.
I use 2" pipe on dumbells cut a bit shorter so that the dumbells roll. Then I grab one in each hand, and do sliding pushups - my hands are on wheels.
I use 2" pipe for just a generally thicker bar than the standard dumbell.
If you want extra grip you can cover them with tennis racket regrip or you can get a bike innertube and chop it up, instant rubberised grip.
If you put pvc pipe over a shopping bag handle you can get two armloads of really heavy groceries and do farmers walks in the shops without looking too silly. I walk home 2km with a nice collection of apples and soda bottles.
The PVC is not strong enough to hold the weight - it does not have to be really, because the weight it carried by the bar. The pipe doesn't suffer at all.