Is there any evidence that the American Indians in the Southwest used cacti/cactus as weapons?

I guess they can hide in a cactus field and watch their enemy’s get prickled.

Not that I know of. They used it for food and liquid.

Cacti are really heavy !
Impractical without something like a catapult to launch a chunk of saguaro at your enemy.
The impact of the mass would probably do more damage than the barbs.

[Mod says] The Question was sent to editing so the OP could clarify his intent. Some of the comments were deleted because the clarification made them extraneous, others because they were just speculation about the deleted comments. Please stay on topic. Thanks!

The spines of some cacti were used as darts for blow guns.

I don’t believe so.

What could they hurl it with that wouldn’t hurt the hurler just as badly?

I can also see a cactus used as a mace of sorts. Don’t if that actually happened or not but I don’t see why it wouldn’t work.

There are smaller, spined cacti that could be hurled, perhaps slingshot style, @dabbler & @Blondesjon. They could also be effective in a thinly covered pit, as they did with bamboo spikes in Asia. Originally the question gave a catapult as as example and that caused the moderation. As darts, as @uberbatman says, and I agree that they could be used as a mace.

A chunk of cholla cactus could be a good size for a slingshot, but I think it would be hard to manage the ammo before you need it. Cholla has the tactical advantage of having barbs on the spines making them especially nasty to remove. Cholla cactus is also known as ‘jumping cactus’ because a section will break off the main plant so easily it can seem that it jumped when you brush by it – easy to harvest if you have impervious gloves or something like that.

Great input, @dabbler! I like your thinking and if there’s a holocaust, I want to be on your team after.

Roger that @ibstubro ! On the other hand, unless it keeps the zombies away, I’d rather not be stuck in a desert in a post-holocaust situation.

Definitely Hawaii, @dabbler. Pre-holocaust we need to meet in Hawaii.
Hopefully high summer.