When working from home we use an Avaya softphone which is kinda annoying as it's not as fast to answer since you need to actually move the mouse over to it and click to answer, vs just picking up receiver on your desk, but it's a compromise to be able to work from home.
At the office we have Nortel Meridian desk phones. Probably the most bullet proof phone system ever.
I heard rumours they want to get rid of that system though, and move to Webex. So maybe at some point we won't have desk phones anymore. I don't know how that's going to work as far as getting outside calls though, it's more of a collaboration tool for internally.