Agave Horrida ssp Horrida
This species of Agave, Native to Mexico, has a single rosette of thick fleshy leaves, with serrated leaf margins. Each leaf tip contains a short and sharp thorn!
Will grow to around 60 cm in diameter. Large flower spikes appear on mature plants. (don't hold your breath though, this may take many years!)
The plants should be kept almost dry during the winter months, only water them to prevent the roots from completely drying out, once a month should be fine.