The responses to Thank You that everyone knows:
You're welcome
Sure
Don't mention it
Anytime!

and many more.

Tonight's lesson:
1. You would've done the same for me.

2. (I) didn't do anything. (It was all you).

3. It was the least I could do. (formal).

4. (sympathise):
Examples:
You helped someone with their heavy shopping.
They say thank you.
You can reply:
Those bags can be really heavy sometimes/ They can cut your fingers / they can dig into your fingers / I struggle as well, sometimes...

You gave someone a lift when it was cold and dark.
They say thank you.
You can reply:
I'd hate to have to get a tube (underground train), taxi / catch a bus in this weather or this time of night.