There are bangers and frag grenades available for sale now. Some even made in Canada!
Yes if you yell grenade and throw, first you're warning your team to keep their heads down, and you may flush your target.
There will be a few times when it may be smarter to slip a frag into an unsuspecting target but if you're in that sort of mil-sim type game then there will most likely be a ROE you can follow.
Airsoft, where nothing is hurt but feelings.