In the Half-Life series, there are many ways you can use weapons, even in ways other than how you’re “supposed” to use them. For example, in HL1, you can place tripmines on walls and stand on them, you can use the gauss gun to jump higher, etc…
Give examples of how you use your weapons in unusual ways. You can mention weapons from other games as well.
In HL2, I use the bugbait a lot and throw them at the combine to distract them, making them easy targets. It never runs out and you can distract an entire group with them, so it’s really handy!