Yes, you can click "Edit" > "Special Characters…" — there you can find all unicode characters (including the emoji) and copy/paste them where you set the label text in Interface Builder.
EDIT:
In Xcode 6 it's "Edit" > "Emoji & Characters"
Xcode 7+: "Edit" > "Emoji & Symbols"
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…