How to extract file name from file list?

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http://stackoverflow.com – Now I have several files, their names include version number, I want to extract their file name only and strip the version number, ES File Explorer_3.0.5.5.apk ES Task Manager_1.4.1.apk Facebook_3.7.apk Gmail_4.6 (836823).apk Google+_4.1.2.51968121.apk Google Play Books_2.9.21.apk Google Search_2.8.8.849369.arm.apk Hangouts_1.2.018 (849105-30).apk Instagram_4.1.2.apk Kingsoft Office_5.7.3.apk Maps_7.2.0.apk Skype_4.4.0.31369.apk Translate_2.8.apk Twitter_4.1.8L.apk WhatsApp_2.11.93.apk YouTube_5.1.10.apk How to do? using vi, sed or awk? Such as extract YouTube or YouTube.apk from YouTube_5. (HowTos)