WelcomePro is a Bukkit plugin that displays a fancy welcome message when a player joins your server. In addition to the welcome message the plugin includes a more practical use because it also displays a configurable Message of the Day. Future plans include allowing the message of the day and the welcome message to be viewed by different groups or set differently for each group.
CustomBanMessage allows you to set a custom message that is displayed to a player when they are banned. The message is fully configurable in the config and this plugin is compatible with any banning system based on the Minecraft one (including Essentials). This is handy if you want players to know where they can appeal their ban or display other information.
LobbyGames is a plugin designed to give players more to do on your lobby server. It allows players to play tic tac toe against each other and to try and beat their highscores in 2048. It also includes a leaderboard and stats and could be used as a perk for donators.
UltimateBackpacks is a fully customizable backpacks plugin. Backpacks are chests that can be right clicked from the hotbar to be opened. This plugin could be useful for factions, prison, survival and many other gamemodes.