Which clearances are issued by ATC without the pilot requesting them?
No clearance is issued without the pilot requesting it. But a request is not just something you do on the radio. The interesting questions here is: how do pilots request something?

The most common way is through a flight plan. By filing a flight plan, the pilot details the planned flight, from departure to destination, via a predefined route, with a requested speed and level. ATC will issue a flightplan clearance prior to departure or prior to entering controlled airspace. This covers the general flight, and basically lets the flight take place.

During the flight, specific details need to be requested by the pilot - such as taxi - but only if the controller is not already aware that the flight is ready for whatever it is they are requesting. For example, during radar vectors for approach, ATC already knows that the flight is requesting approach at their destination (since the destination is noted in the flightplan), so ATC will clear the flight for approach without needing the pilot to explicitally request it. Same goes for landing clearance. The pilot does not have to explicitally say "request to land", because this is already a part of the flight plan. ATC will automatically issue a landing clearance when appropriate.

ATC can issue instructions or clearances to flights that deviate from their flightplan if needed for safety or efficiency reasons. For example, ATC may instruct a flight to change level due to traffic ahead on the same level. But the flight plan is always the basis for all clearances.