I would put retreiving of cvar values in plugin_cfg() personally so that other configs are executed before you retrieve the value.
EDIT: Ok, so I tested some things. I created a cvar in one plugin and tried retrieving the pointer in another (both in plugin_init and in plugin_cfg). The cvar did not exist in plugin_init when first starting the server. After that it existed in both. FYI.
Therefore any get_pcvar_*() functions will send an error when used for a non-existant cvar.
Also, in my test it seems that amxx.cfg and server.cfg were executed after plugin_cfg() which seems strange to me intuitively.
EDIT2: Just tried it with mp_friendlyfire and is always 0 when you first start the server (cause by my last statement above). That sucks. Wish there was a forward executed after all native .cfg files were executed.
EDIT3: There is no public function named "ResetHUD". You should be seeing errors because of this.