Less Than three should make a heart emoji.
<3
Let’s try some more:
Less Than <
Greater than >
Less or equal ≤
Greater or equal ≥
Open bracket [
Closed bracket ]
Open brace {
Closed brace }
Forward slash /
Back slash \
There might be more, but I haven’t found them yet.
<3
I ampersand lieutenant semi colon three you too.