I have a friend who often typoes "yeah" as "yeha", which is kind of cute because it looks like a miniature version of "yeehaa!"

I tend to type "possible" instead of "possibly" far too often, due to using the former word far too often in academic writing. Some key combinations become ingrained in your muscle memory over time, it can be hard to type something similar but different...

Occasionally, I'll type "who're" without the apostrophe, but thankfully I always spot that in time and never actually post it in a thread.