This is my personal vehicles prefab pack that I've built and tweaked over the years. It includes nearly every vehicle that shows up in vanilla Half-Life. I've tried to keep things as close to realistic as possible, including scaling, so things may seem different from what people are used to. No custom textures or sounds are used.
M924 Cargo Truck
M923 Flatbed Truck
M2A3 Bradley Infantry Fighting Vehicle (active/destroyable and inactive variants)
M1A2 Abrams Main Battle Tank (active/destroyable and inactive variants)
1990s Ford Explorer, BMRF (hollow/destroyable and low-poly solid)
1990s Ford F-150, BMRF Maintenance (hollow/destroyable)
Red BMRF Switcher Locomotive
BMRF Flatbed Locomotive
BMRF Unpowered Flatbed Car
BMRF Transit Car
Fairchild Republic A-10 "Warthog" Ground Attack Craft (because why not)
Numerous BMRF monorail sections (not pictured) -- includes junctions, curves, sidings, and straight sections
- NOTE: The Bradley and Abrams are tuned for realism, so feel free to adjust them to your tastes.