Un-killables?

Ok my sister the plant killer has asked me to put in some cacti for her. As I am planting mostly eceheverias and low-height stuff I was thinking of planting some columnar species but I need super-unkillable guys. Now I actually have access to trichocerues (spach maybe) cuttings which I think should be okay.
Would cereus peruvianis be suitable? I can but cuttings of that pretty cheaply online. My opuntias are a bit spindly at the moment and the area is not at all sheltered from wind.
Or should I just plant some echinopsis? I am a bit worried about snails with those.

Echeverias are mostly pretty tough and seem to handle both the wet and dry pretty well. Cereus peruvianus is one of the more common columnars in gardens around Melbourne, so I think that should be able to handle most situations. Spachs are also nice; there's also a strongly clumping Trich (possibly huasca?) that seems to be a fairly common garden plant. Pachanoi is an option, but you'll probably pay a bit of a premium to get decent-sized specimens. If the location gets a bit of sun then some of the larger Opuntias could work nicely. The common "feral" one - I think it's ficus-indica - could be a nice option to give some structure to the garden.

It gets tonnes of sun actually, so thanks Lach, I was a bit worried about planting some of the bigger ones.
I actually , managed to fill a whole lot of it with some larger succulents too that I found in various parts of the garden, so i think two columnar species should do it.

This thread has given me an idea...

Around much of Melbourne, it's quite common to see older, well established gardens with cacti growing quite happily alongside "normal" garden plants. Presumably, these cacti receive no special treatment and yet are absolutely thriving. These cacti strike me as great candidates for making a list of "unkillable" plants suitable for the outdoor garden.

So, while you guys are driving or walking around the suburbs and you see a garden with a cactus growing happily amongst the foliage, see if you can ID it so it can be added to the list... if you can't ID it, see if you can get a photo of it (with the owners permision, of course).

We were up at the house we're building the other day and I had a peek around the display homes and was a bit surprised to see some happy cacti in the front garden! These places have been up at least eighteen months. I took some pics, I think it's a tricho of some sort, someone help me out here









And I took a couple of pics of some succulents just because i thought it was a really nice garden, they've mixed it up with some native plants and it looks great

cereus, opuntia, trichocereus pachanoi etc, all unkillablezz

This is an amazing potted front garden I stumbled across is se melbourne

awesome... the huge notocactus [?] in the back and the spined columnar with reddish spines on top are the highlights!

I don't know the proper name for the huge one, I know the common name is golden torch and i reckon it must be about 30 years old, I have a pair of ten year olds that are only about 40 or 50 cms!