In 13w42a, while in a creative world that was raining, I adjusted the sound slider for weather and the game crashed. All other sliders seemed to work fine. Crash report to follow. Game is completely vanilla.
Update: happens when you adjust the weather sound slider at all not just when raining.

---- Minecraft Crash Report ----
// Everything's going to plan. No, really, that was supposed to happen.

Time: 10/17/13 8:09 PM
Description: Updating screen events

java.lang.NullPointerException: Updating screen events
at bsl.a(SourceFile:306)
at bsl.a(SourceFile:112)
at bsr.a(SourceFile:191)
at azp.a(SourceFile:793)
at bcd.c(SourceFile:117)
at bbw.a(SourceFile:169)
at bbw.d(SourceFile:236)
at bbw.k(SourceFile:211)
at ayw.o(SourceFile:1296)
at ayw.ac(SourceFile:749)
at ayw.e(SourceFile:700)
at net.minecraft.client.main.Main.main(SourceFile:103)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Stacktrace:
at bsl.a(SourceFile:306)
at bsl.a(SourceFile:112)
at bsr.a(SourceFile:191)
at azp.a(SourceFile:793)
at bcd.c(SourceFile:117)
at bbw.a(SourceFile:169)
at bbw.d(SourceFile:236)
at bbw.k(SourceFile:211)

– Affected screen –
Details:
Screen name: bcc

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [biw['willderphil'/103, l='MpServer', x=-1703.34, y=5.62, z=469.62]]
Chunk stats: MultiplayerChunkCache: 225, 225
Level seed: 0
Level generator: ID 01 - flat, ver 0. Features enabled: false
Level generator options:
Level spawn location: World: (-1738,4,462), Chunk: (at 6,0,14 in -109,28; contains blocks -1744,0,448 to -1729,255,463), Region: (-4,0; contains chunks -128,0 to -97,31, blocks -2048,0,0 to -1537,255,511)
Level time: 2341322 game time, 9819 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: true), thunder time: 0 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
Forced entities: 76 total; [rk['Painting'/77, l='MpServer', x=-1706.06, y=8.00, z=523.00], rk['Painting'/76, l='MpServer', x=-1709.00, y=8.00, z=526.94], rk['Painting'/70, l='MpServer', x=-1715.00, y=8.00, z=526.94], rk['Painting'/69, l='MpServer', x=-1716.94, y=10.50, z=522.00], rk['Painting'/35, l='MpServer', x=-1752.50, y=6.00, z=468.94], rk['Painting'/34, l='MpServer', x=-1752.50, y=7.50, z=468.94], rk['Painting'/25, l='MpServer', x=-1763.50, y=6.50, z=468.94], uw['Cat'/21, l='MpServer', x=-1777.03, y=4.00, z=486.69], ux['Pig'/23, l='MpServer', x=-1774.91, y=4.00, z=407.75], rk['Painting'/26, l='MpServer', x=-1761.50, y=5.50, z=468.94], rk['Painting'/25, l='MpServer', x=-1763.50, y=6.50, z=468.94], rk['Painting'/33, l='MpServer', x=-1751.50, y=6.50, z=468.94], up['Chicken'/24, l='MpServer', x=-1775.53, y=4.00, z=427.56], uv['Mooshroom'/27, l='MpServer', x=-1765.91, y=4.00, z=470.94], rk['Painting'/26, l='MpServer', x=-1761.50, y=5.50, z=468.94], rk['Painting'/36, l='MpServer', x=-1754.50, y=5.50, z=468.94], uw['Cat'/29, l='MpServer', x=-1767.94, y=4.00, z=470.31], rk['Painting'/37, l='MpServer', x=-1753.50, y=4.50, z=468.94], uw['Cat'/28, l='MpServer', x=-1769.69, y=4.00, z=472.06], uw['Cat'/30, l='MpServer', x=-1768.25, y=4.00, z=471.41], rk['Painting'/34, l='MpServer', x=-1752.50, y=7.50, z=468.94], rk['Painting'/35, l='MpServer', x=-1752.50, y=6.00, z=468.94], rk['Painting'/33, l='MpServer', x=-1751.50, y=6.50, z=468.94], ux['Pig'/38, l='MpServer', x=-1745.50, y=4.00, z=470.09], ux['Pig'/39, l='MpServer', x=-1747.91, y=4.00, z=470.09], rk['Painting'/36, l='MpServer', x=-1754.50, y=5.50, z=468.94], rk['Painting'/37, l='MpServer', x=-1753.50, y=4.50, z=468.94], up['Chicken'/42, l='MpServer', x=-1758.00, y=4.00, z=511.53], vt['item.item.egg'/43, l='MpServer', x=-1755.09, y=4.13, z=513.81], uq['Cow'/40, l='MpServer', x=-1754.13, y=4.00, z=470.97], uy['Sheep'/41, l='MpServer', x=-1750.94, y=4.00, z=470.84], wb['entity.MinecartRideable.name'/46, l='MpServer', x=-1729.47, y=4.34, z=443.34], vz['entity.MinecartFurnace.name'/47, l='MpServer', x=-1742.38, y=4.34, z=438.09], wb['entity.MinecartRideable.name'/45, l='MpServer', x=-1737.81, y=4.34, z=444.50], uy['Sheep'/51, l='MpServer', x=-1733.56, y=4.00, z=504.44], wb['entity.MinecartRideable.name'/50, l='MpServer', x=-1737.84, y=4.34, z=481.59], wb['entity.MinecartRideable.name'/49, l='MpServer', x=-1741.84, y=4.34, z=445.13], vv['entity.MinecartChest.name'/48, l='MpServer', x=-1736.00, y=4.34, z=435.72], wb['entity.MinecartRideable.name'/55, l='MpServer', x=-1723.53, y=4.34, z=439.97], uy['Sheep'/54, l='MpServer', x=-1720.19, y=4.00, z=406.88], rc['entity.ItemFrame.name'/59, l='MpServer', x=-1720.50, y=5.50, z=475.94], wb['entity.MinecartRideable.name'/58, l='MpServer', x=-1715.25, y=4.34, z=443.56], wb['entity.MinecartRideable.name'/57, l='MpServer', x=-1720.91, y=4.34, z=434.47], wb['entity.MinecartRideable.name'/56, l='MpServer', x=-1718.63, y=4.34, z=436.59], rc['entity.ItemFrame.name'/63, l='MpServer', x=-1716.50, y=5.50, z=475.94], rc['entity.ItemFrame.name'/62, l='MpServer', x=-1717.50, y=5.50, z=475.94], rc['entity.ItemFrame.name'/61, l='MpServer', x=-1718.50, y=5.50, z=475.94], rc['entity.ItemFrame.name'/60, l='MpServer', x=-1719.50, y=5.50, z=475.94], un['Bat'/68, l='MpServer', x=-1721.39, y=4.84, z=490.05], rk['Painting'/69, l='MpServer', x=-1716.94, y=10.50, z=522.00], rk['Painting'/70, l='MpServer', x=-1715.00, y=8.00, z=526.94], rc['entity.ItemFrame.name'/64, l='MpServer', x=-1715.50, y=5.50, z=475.94], rc['entity.ItemFrame.name'/65, l='MpServer', x=-1714.50, y=5.50, z=475.94], rc['entity.ItemFrame.name'/66, l='MpServer', x=-1713.50, y=5.50, z=475.94], rc['entity.ItemFrame.name'/67, l='MpServer', x=-1719.94, y=5.50, z=485.50], rk['Painting'/76, l='MpServer', x=-1709.00, y=8.00, z=526.94], rk['Painting'/77, l='MpServer', x=-1706.06, y=8.00, z=523.00], un['Bat'/78, l='MpServer', x=-1692.07, y=22.55, z=431.13], un['Bat'/79, l='MpServer', x=-1684.83, y=5.69, z=514.48], un['Bat'/72, l='MpServer', x=-1691.24, y=6.51, z=407.47], un['Bat'/73, l='MpServer', x=-1696.25, y=23.10, z=439.59], un['Bat'/74, l='MpServer', x=-1696.25, y=23.10, z=439.25], un['Bat'/75, l='MpServer', x=-1696.66, y=22.76, z=440.01], uy['Sheep'/84, l='MpServer', x=-1686.07, y=4.00, z=510.85], un['Bat'/87, l='MpServer', x=-1664.33, y=4.15, z=436.33], un['Bat'/86, l='MpServer', x=-1652.34, y=4.00, z=447.49], un['Bat'/81, l='MpServer', x=-1676.75, y=9.10, z=396.66], un['Bat'/80, l='MpServer', x=-1676.75, y=7.84, z=399.39], un['Bat'/83, l='MpServer', x=-1673.84, y=7.26, z=435.53], un['Bat'/82, l='MpServer', x=-1676.75, y=8.10, z=401.75], un['Bat'/93, l='MpServer', x=-1628.56, y=4.02, z=493.41], uy['Sheep'/92, l='MpServer', x=-1636.84, y=4.00, z=504.13], ux['Pig'/88, l='MpServer', x=-1648.94, y=4.00, z=503.81], un['Bat'/91, l='MpServer', x=-1636.49, y=4.55, z=482.04], uy['Sheep'/90, l='MpServer', x=-1640.72, y=4.00, z=461.81], biw['willderphil'/103, l='MpServer', x=-1703.34, y=5.62, z=469.62]]
Retry entities: 0 total; []
Server brand: vanilla
Server type: Integrated singleplayer server
Stacktrace:
at bir.a(SourceFile:284)
at ayw.b(SourceFile:1928)
at ayw.e(SourceFile:709)
at net.minecraft.client.main.Main.main(SourceFile:103)

– System Details –
Details:
Minecraft Version: 13w42a
Operating System: Windows XP (x86) version 5.1
Java Version: 1.7.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 52734736 bytes (50 MB) / 123281408 bytes (117 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 8108 (454048 bytes; 0 MB) allocated, 2 (112 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 13w42a
LWJGL: 2.9.0
OpenGL: GeForce 9500 GT/PCIe/SSE2 GL version 3.3.0, NVIDIA Corporation
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 738 (41328 bytes; 0 MB) allocated, 20 (1120 bytes; 0 MB) used
Anisotropic Filtering: Off (1)