Reading some discussions, many KSC players know there are parts that aren't "interesting" because they are flowed.
Mk1-2 Command Pod is way too heavy
Mk2 Lander-can is too heavy
ISRU may be too light
PPD-12 Cupola Module is too heavy
RC-L01 Remote Guidance Unit is too heavy
Kerbodyne ADTP-2-3 could hold some fuel
EAS-4 Strut Connector is too heavy and too draggy (usually used to parry joints weakness)
Cubic Octagonal Strut is way too light (