Keurig's cheapest, most basic brewer, the K-Express measures less than 5" wide (just like the K-Mini and K-Slim) with 8-12 oz brew sizes, Strength Control, a 7" cup clearance. For compact Keurigs, it beats the K-Mini easily.
Keurig's first machine designed to brew lattes and cappuccinos, the Rivo has since been discontinued and replaced by the Keurig K-Cafe and K-Latte. We'd go with one of those, but you can still find the Rivo online.
If you're looking for total customer convenience, the Keurig K3500 is your machine. Its sleek design and hi-res touchscreen scream quality, and 5 brew sizes, hot water on demand, and pod auto-eject make operation easy.