In Half-Life: Team Fortress Classic, a squeeze point on maps such as Dustbowl where it is a manner of course when attacking to collectively receive literally 30 or more grenades from the defender, along with various other types of fire, in particular from sentry gun nests.
The best examples I can think of are the starts of the second and third stages of Dustbowl. Either can easily add 10 deaths to an aggressive attacker's tally.
Oftentimes, the only useful course of action is perseverance and return fire, particularly your own grenades. While standard grenades should work just fine, MIRVs, concs, and napalm are much more efficient. Also, better armed and armored classes last a few seconds longer in these, so the most important classes for running grenade gauntlets are heavy weapons guys, soldiers, and demomen. Scouts, snipers, and medics, despite their speed, get blasted to smithereens almost instantly.