led lights flickering/cutting on and off?

okay, i'm sure this has been discussed to death but i'm at work and don't have alot of time to search. i figure i'll ask and check back later and see what the answers are.

whats with LED flashlights? with the exception of my 3 D cell mag LED, every light i have will flicker and cut off and on. i have to push the off/on switch multiple times, or turn the battery cap or shake the light to get it to quit. some times i turn the flashlight on and it won't come on untill i mess with it for a minute. it was a problem on my 3AA streamlight, it was a problem with my streamlight stylus, its a problem with my surefire 6p led, it's been a problem with a $25 rayovac i bought at walmart and its been a problem with some of the cheaper LED's i've bought.
on some of the lights i've cleaned the batteries and connections with scotch brite and it made no difference.

Yep, flickering / non-working lights are a regular topic posted by newcomers.....

Open up each light, tighten the tailcap / switch

Clean and lube threads

Check springs for proper contact

Check for charged batteries [this is #1 actually]

Most of the regulated lights on the market nowadays will "pulse, flicker, strobe, flash" or in some similar manner alert the user that the battery is getting too low to maintain the light. Replace or recharge the batteries.

This is especially the most likely cause since you said you have already cleaned the connections.

Yep like the others have said,when my Microstream starts a little dance it needs more food.