There are end cab switchers still being used in yards, but you're starting to see more GP38-2s/3s out there now. Conrail's Sterling Yard now has a NS GP38-3 (converted GP40-2) working as the yard switcher.
Some big yards have the odd SD-38s (could also be a de-turbo'd SD-40), or regular SD-40s even. If you're talking a small yard, could be a chop-nosed GP7/8/9/10. EJ&E's Lang Yard has a couple of ex-DMIR SD-9s.
CSX's Willard Yard uses a GP38-2/slug set for the hump as well as flat switching. They also use road power to build a train; have had many of those block the view of the diesel house and the rest of the yard as the crew works to build their train.
NS's Bellevue Yard uses a high-nosed SD40-2 mated to a Baldwin slug as the hump power. I don't recall seeing what they use to flat switch....
I should also note that while looking into UP's Global III intermodal yard, there was a SD40-2 doing the switching.
Kennedy