How to insert emoticons in LaTeX?

If you use xelatex or lualatex, then

\documentclass{article}
\usepackage{fontspec}
\setmainfont{Symbola}
\begin{document}
😺
👅 
\end{document}

should produce black-and-white emoji letters in Symbola font, which is available from http://users.teilar.gr/%7Eg1951d/ or standard package repositories in some Linux distros (e.g. Ubuntu). The MS Windows emoji font can also be used by \fontspec{Segoe UI Emoji}[RawFeature={ccmp,dist}] in place of \fontspec{Symbola}.

Unfortunately the color (emoji) fonts are not supported by the standard lualatex or xelatex. harflatex and luahblatex can typeset color emojis using

\documentclass{minimal}
\usepackage{harfload}
\usepackage{fontspec}

\begin{document}
\noindent
\fontspec{Noto Color Emoji}[RawFeature={mode=harf}]
☃⛄💩🏩🏨🕐🕜💫🀇🍣🤮🤯👨‍👩‍👧‍👦\quad 👩‍❤️‍💋‍👨
\end{document}

harflatex and luahblatex can be installed from TeXLive Contrib at https://contrib.texlive.info/ as of July 2019.

The above is learnt from https://tex.stackexchange.com/questions/497403/how-to-use-noto-color-emoji-with-lualatex/500180 with a bit of my own investigation.

I know at least two partial ways:

First:

$\ddot\smile$

Second:

\usepackage{wasysym}
\smiley
\frownie

Or you can use images (as mentioned in other replies).

What's against a simple {\tt :-)}?