I've never played Half-Life, but I have to admit that the game's gravity gun strikes me as perhaps the second-most fun video game method of destroying things.
The most fun way, of course, is to crash into things in a game with collision physics that inflict damage while you have an invulnerability cheat going. Well, crashing is just generally fun in games.*
*In-game driving behavior does not reflect on my real-world driving behavior. My parents call me a sunday driver and old people tear past me on the road.