Well with the default i was quite bored so i made some new muzzle flashes
i hope u enjoy them
Made in Photoshop

Paste the 'effects' folder into:
...SteamApps\[your username]\counter-strike source\cstrike\materials

If u dont like them just delete the 'effects' folder, but if u have more things in there just delete "muzzleflashX.vtf" and "muzzleflash4.vtf"

Neemz
btw my CS:S alias is "Worst player in history" (as of this date) 