Secure by Design

Horticulture Week (UK) reported a local police force has suggested design and plant species to help keep the backyard from bunglers.
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In Singapore's context, some plants (with the exception of the obvious cactus) that serve the same purpose would include:

Suitable for small spaces

Bougainvillea
Photo credit: Joel Abroad - https://www.flickr.com/photos/40295335@N00

Caesalpinia pulcherrima (Peacock Flower)
Photo credit: kimubert - https://www.flickr.com/photos/treevillage

Duranta erecta or Duranta erecta 'Variegata' (Golden Dew-Drop)
Photo credit: Hildegard Chen - https://www.flickr.com/photos/hildegardtschen

Lasia spinosa (Geli-geli)
Photo credit: Cerlin Ng - https://www.flickr.com/photos/89906643@N06

Pandanus pygmaeus (Dwarf Screwpine)
Photo credit: Ahmad Fuad Morad - https://www.flickr.com/photos/adaduitokla

Suitable for large spaces

Bambusa multiplex or Bambusa vulgaris (Bamboo small or Bamboo large, respectively)
Photo credit: techieoldfox - https://www.flickr.com/photos/techieoldfox

Oncosperma tigillarium (Nibong Palm)
Photo credit: Forest and Kim Starr - https://www.flickr.com/photos/starr-environmental

Licuala spinosa (Mangrove Fan Palm)
Photo credit: author

Zamia furfuracea (Cardboard Palm)
Photo credit: Forest and Kim Starr - https://www.flickr.com/photos/starr-environmental