After reading the Winter15 Release Notes. Some of my favourites so far
*Deploy Your Components in Less Time (Pilot)
http://releasenotes.docs.salesforce.com/en-us/winter15/release-notes/rn_quick_deployment.htm
*Run More Future Methods and Callouts
http://releasenotes.docs.salesforce.com/en-us/winter15/release-notes/rn_apex_limits_callout_future.htm
*Queueable Interface
http://releasenotes.docs.salesforce.com/en-us/winter15/release-notes/rn_apex_queueing_jobs.htm
*Remote Objects is generally available
http://releasenotes.docs.salesforce.com/en-us/winter15/release-notes/rn_vf_remote_objects_ga.htm
*Dupe Alerts
http://releasenotes.docs.salesforce.com/en-us/winter15/release-notes/rn_general_dedupe.htm#rn_general_dedupe
*Event log files
http://releasenotes.docs.salesforce.com/en-us/winter15/release-notes/rn_forcecom_security_elf.htm#topic-title
Winter 15 - My favorites