Contrasting Ideas:
* But
* Yet
* Nevertheless
* Nonetheless
* On the other hand
* In contrast
* Despite this
* Regardless
* Still
* Even so
* Although
* Though
* Whereas
Introducing a Qualification:
* However
* But
* Yet
* Still
* Nevertheless
* Nonetheless
* On the other hand
* In spite of this
* Despite this
Other Options:
* In any case
* Anyway
* Anyhow
* Be that as it may
* At any rate
The best choice will depend on the specific sentence and the nuance you want to convey.