Hitmarker

You can use hitmarkers to locate enemies by shooting them through walls.

Source: wiktionary

If you see a hit marker from your grenade/tactical, you’ll know where they are (generally), even if you don’t get the kill outright.

Source: wiktionary

While you might expect something called Hardcore mode to toss away crutches like the HUD, hitmarkers, and anything else that's remotely useful, it doesn't.

Source: wiktionary