List of emotes I can use at SteamGifts/SteamTrades?

I believe they're simply emojis, and not SG/ST specific.

• Full list from which you can copy characters from the third column in the table.
• You can use a web-based emoji keyboard.
• There's a Chrome browser plugin.
• Mobile operating systems and browsers likely have them easily/obviously accessible. In recent builds of Windows 10 (last year or so), you can use the Windows key + '.' or Windows key + ';' to bring up a pop-up keyboard. On Macs, use Cmd + Ctrl + Space.