So I don't know if this warrants a whole thread, but since it just happened I figured I'd share...
One of my projects is a remote control for my LED strip water jug lamp, and today I went to reprogram it (seems to be noticing too much noise in the potentiometer & runs down the coin cell battery with frequent nRF24L01+ RF transmits) and it worked as expected; I have GND, TEST and RESET broken out (not Vcc) so only those 3 were connected to my launchpad.
I turned off the potentiometer-RF-update feature temporarily while I figure that out, then reflashed the MCU (it's a G2553 TSSOP-20). Nothing strange so far.
...Then I disconnected the jumper wires, turned the board over and realized the battery was missing! The whole project was powered parasitically through the RESET/TEST lines and programmed just fine. Guess I could go back and verify that it flashed correctly, but so far the firmware behaves as expected so I assume it's fine.
PS- This mainly shows that I need some coffee!