Hello,
At current time, using VoxelSniper and xAuth together generates an error when trying to use any xauth command. This is not my error log, as I have deleted my error since then, but this someone else's reproduction of the problem.

2013-02-26 21:49:18 [SEVERE] null org.bukkit.command.CommandException: Unhandled exception executing command 'login' in plugin xAuth v2.0.26 at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:186) at org.bukkit.craftbukkit.v1_4_R1.CraftServer.dispatchCommand(CraftServer.java:514) at net.minecraft.server.v1_4_R1.PlayerConnection.handleCommand(PlayerConnection.java:980) at net.minecraft.server.v1_4_R1.PlayerConnection.chat(PlayerConnection.java:898) at net.minecraft.server.v1_4_R1.PlayerConnection.a(PlayerConnection.java:853) at net.minecraft.server.v1_4_R1.Packet3Chat.handle(Packet3Chat.java:44) at net.minecraft.server.v1_4_R1.NetworkManager.b(NetworkManager.java:290) at net.minecraft.server.v1_4_R1.PlayerConnection.d(PlayerConnection.java:113) at net.minecraft.server.v1_4_R1.ServerConnection.b(SourceFile:39) at net.minecraft.server.v1_4_R1.DedicatedServerConnection.b(SourceFile:30) at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:598) at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224) at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:494) at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:427) at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849) Caused by: java.lang.NoSuchMethodError: com.martiansoftware.jsap.CommandLineTokenizer.tokenize([Ljava/lang/String;)[Ljava/lang/String; at com.cypherx.xauth.commands.LoginCommand.onCommand(LoginCommand.java:38) at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ... 15 more

How can it be made so that both plugins play nice with one another?
Thank you.

As far as I can see it is impossible that sniper causes this error. Does xAuth work without sniper on the server? Also, we need your sniper version, Bukkit version, Java version and some more information in order to help you properly. Please check the README here on github.

Yes, it works without VS installed. I'm sorry I didn't supply this information beforehand, but here it is:

• Bukkit 1.4.7 RB
• java version "1.7.0_09"
  -- Java(TM) SE Runtime Environment (build 1.7.0_09-b05)
• VoxelSniper 5.168.5-SNAPSHOT (I am unsure of the build we were using at the time)
• Xauth 2.0.26

Other plugins currently installed: TimTheEnchanter, WorldBorder, Bending, WorldEdit, MotdManager, Vault, BanHammer, PermissionsEx, Multiverse-Core, LogBlock, LWC, WorldGuard, BetterAnnounce, RegCheck, KeepItems, SurvivalGames, BookRules, EpicBossRecoded, SkylandsPlus, VariableTriggers, SimpleSpleef, Modifyworld, Votifier, PlayerSkulls, WeatherMan, MobArena, mcMMO, Essentials, Citizens, ChatManager, ServerSigns, Multiverse-Portals, Multiverse-Inventories, SkyFall, BOSEconomy, xAuth, BattleArena, DtlCitizensTrader, ArenaPaintball

I realize that xAuth might be the one at fault for causing the incompatibility, but you have to start your search somewhere, right?

Edit:
Also, one of my staff members brought this to my attention:
http://dev.bukkit.org/server-mods/xauth/tickets/253-voxel-sniper-xauth/

So does that mean xauth is at fault?