Three Four here.
What is the bug: Piston + Sponge
1. Place sponge in lava
2. Use a piston to move sponge over 5 blocks
3. Without block-updating the sponge-air-blocks-that-used-to-be, fill in and dig out the sponge-air-blocks-that-are-now
4. That area no longer has any lava
5. Repeat, so an area of any size can be cleared out using only one sponge.
How did you discover this bug:
Random fiddling around.
How could it possibly be solved:
Make sponges not be pushable by pistons, or make moving/breaking a sponge cause a block update to all blocks within 2 blocks of it. The latter solution will also solve the glitch/quirk that a sponge, when broken, leaves the air until the lava is block updated.
Anything else you want to say about it:
Nope.
What is the bug:
Vanished ops can be seen via /glist
How did you discover this bug:
Doing /glist and noticing an op was on that wasn't on /list and concluded that they were vanished
How could it possibly be solved:
Fix /glist to not include vanished ops
Anything else you want to say about it:
Nope.
What is the bug:
/time is weird, it increments one minute every second and, (consequentially) does not show the correct server time
How did you discover this bug:
Doing /time by instinct to help me figure out timezones, then realizing that it was horribly wrong
How could it possibly be solved:
Fix or disable /time
Anything else you want to say about it:
Nope.
What is the bug:
Piston head blocks, when melted, drop the piston, thus enabling people to easily build in lava using pistons since the piston head blocks can be built off of
How did you discover this bug:
Random fiddling around
How could it possibly be solved:
Make Block 34 melt, not break.
Anything else you want to say about it:
Same thing happens to beds.