To all those who don't have the time to type in the entire word and all they write is MT, I'm typing it here so you can copy and paste the full beracha. No longer the need to waste your time and type the full thing!
Nusach Sefard: Mazel tuv Nusach Ashkenaz: Mazel toiv Nusach Eidos Hamizrach: Mazal tov Good old way: Mazel tov SUPER EXCITED: MAZEL TOV!!!!