Haworthia retusa
Native range: South Africa
Known names: Window succulent
Hardiness: Best kept above freezing
Mature Size: ~5" tall, 5" wide
Light: Bright light, indirect sun, (direct sun can burn the plant)
Water: If possible, avoid much winter water, maybe once a month. Water more often during summer.
Soil: Fast draing, coarse succulent soil
Dormancy Period: Summer
Pet-Safe: Yes
Plant Size: Grown in 2.5" pot
 
Haworthias, in the wild, generally grows underground with their "windows" poking up slightly to catch some sun. These succulents will actually do poorly if exposed to too much sun so it is best to grow them either with morning sun only or dappled sun or somewhere shaded away from the hot sun. 
Avoid overwatering in Summer; they'll end up rotting if the soil is wet and the weather is hot.