Announce your favorite marine mammal to be a dolphin. State the reason being “dolphins sometimes engage in homosexual activity."
Write to the Ellen Show and maybe she could announce it for you.
Put an “I’m gay” message in an empty bottle and put it in their bathtub.
Use sign language or tell them your favourite letters in the alphabet are "G", "A" and "Y".
Play hangman. When it’s your turn make the phrase they have to guess be “I’m gay”.
Put together a scavenger hunt, where the clues are all gay related and lead to you expressing your feelings.
Record your voice saying “I’m gay” in a build-a-bear and give it as a gift.
Invite them over to your place, then have them follow you to a closet. Enter it and then count to 3 and then jump out and shout "I'm gay". This can also be done if invited to their house.
Pretend to have a serious conversation about how you got a girl pregnant and how you have to marry her and move in. Then go "just kidding, I'm totally gay".
Bring them over your place for a catch up lunch where you cook a pizza and have the toppings (i.e. olives) spell "I'm gay". This also works with a cake and the icing saying "I'm gay".
Ask if you can borrow their phone pretending yours is out of batt. Change your name on their phone to say "First name: your name, Surname: is gay", give them back their phone and then call them.
Ask them if they ever plan on getting married and then just say how you totally would once it's legal.
Play a game of charades and have them guess it. Or play the "what if" game and after a few random ones say "what if I'm gay?"