You know that Medic said "Impossible" somewhere. You've heard it in other people's SFMs. But where can you find the audio file to use for yourself?

Well, here's some resources to hopefully make your job easier.

[This is by no means a comprehensive list; feel free to comment any resources you find helpful and I might add them to the guide.]

https://wiki.teamfortress.com/wiki/Responses#Class_responses

A good general purpose resource. Ctrl-F and type whatever words you're looking for.

Things to keep in mind when doing Ctrl-F:

• Accents: For example, Medic's responses will have words like "Vhat", "Zat", and "Ve", so search by those rather than the proper English spelling.
  
• Sounds: Responses may be described as [laughter] or [scream], so search by those words rather than something like "hahaha" or "aaaah".
  
• Punctuation: Consider punctuation too. If "Ah jeez" returns 0 results, that's not because the audio's not there, but because you missed a comma there.

Worst comes to worst, just scroll down the page and look at every line one-by-one.

https://wiki.teamfortress.com/wiki/Voice_commands#Voice_commands

All the common voice commands you'll constantly hear in-game.

https://wiki.teamfortress.com/wiki/Taunts#Taunts_by_class

This is something I didn't consider when I first started looking for dialogue. The TF2 Wiki helpfully provides dialogue descriptions for each merc's taunts too.

https://wiki.teamfortress.com/wiki/Movies#Movies

The Wiki also helpfully provides video transcripts for the official TF2 movies. This is where you can find dialogue that isn't actually in the game, meaning you'll have to get the audio file from online instead of through SFM.

Over the years, a few VAs have made their own unofficial voicelines for the community.

Famous examples include the Scout singing 'All Star' and, more recently, "Medic gaming" and "Sniper gaming".

Scout's voice actor, Nathan Vetterlein, has his own YouTube channel where he sometimes does voice acting requests: https://www.youtube.com/channel/UCHccuAPqKRjMu5oVJQt_nbw
So that's pretty neat.

And here's your last resort with its own advantages and disadvantages compared to AI-generated voicelines. This is what TF2 animators used long before AI reared its head, and many/most animators still swear by this method. Here's a funny video comparing the two: https://www.youtube.com/watch?v=bXkRj-UcWVM

It certainly has its charm, and good sentence mixing will sound much closer to the TF2 mercs than anything AI can create. I won't go too in-depth into it, but you'll need an audio editor program like Audacity and a bunch of voicelines you'd like to mix and match. Mixing words from separate voicelines is the most basic step, and some people also mix phonemes to create new words.

Your viewers will appreciate the extra effort.

There are various TTS websites that offer AI-generated dialog for the TF2 mercs. I haven't used these myself, but they've gained a certain notoriety recently. These are always lower quality than the real voicelines (and lazier than sentence mixing), but they can work in a pinch, though I wouldn't really recommend relying on these too much.

• 15.ai: probably the most well-known one
  
• Uberduck: I haven't heard anything good about this one, but it exists