One of the critical things I use example.com for is triggering wifi login portals as it doesn't not use SSL. Certificate pinning and all that fancy stuff has made it so the browser has an absolutely awful time figuring out what to do when https://google.com does not present itself as the same host it was earlier.
I like using http://neverssl.com/ for that... easy to remember (although I guess example.com was as well).
Same server also has an endpoint for that: http://no-tls.testserver.host. Sends RST for any attempted TLS connections, so clients always fall back to plain HTTP.
Also as a _long_ list of other specialist TLS endpoint configurations if you're interested, which can be arbitrarily combined, see https://testserver.host/#tls-endpoints.
That gives neat tricks like https://tls-v1-2--expired--incomplete-chain--http2.testserve...: only accepts TLS 1.2, then sends an expired certificate but fails to send the intermediate cert for the chain (so the client must infer it) and then negotiates HTTP/2 for the connection on top. Fun!