Many source plugins have already added support for the Pipeline feature, while others can be upgraded to support Pipeline through some code changes to utilize some newer APIs.
git): supported as of 2.3; native
gitstep also bundled
subversion): supported as of the Subversion Plugin’s v 2.5; native
svnstep also bundled
mercurial): supported as of 1.51
p4, not the older
perforce): supported as of 1.2.0
copyartifact): JENKINS-24887 in 1.34
API to integrate build wrappers: JENKINS-24673
parallel-test-executor: supported with
splitTestsstep since 1.6
mailer: JENKINS-26104 in Pipeline 1.2
The most up to date list on available steps can always be found in the Pipeline snippet generator. The snippet generator is located at the bottom of the configuration page for every Pipeline job. Steps offered by a compatible plugin will appear in the snippet generator once the compatible plugin is installed.
There are some plugins which have not yet incorporated support for Pipeline. Guides on how to add this support, as well as their relevant Jenkins JIRA tickets can be found in the Pipeline Plugin GitHub documentation.