Reverend - Yeah I hate that. Thats why I put a back door on all my buildings. (though funny, I've not seen as many Creepers lately. I wonder if they're all spawning in an underground hole somewhere?)
If you have an excess of arrows, how about a security system?
A dispenser, a few bits of red dust and a button.
Well, I was just thinking a tent would be a nice portable alternative to carrying a bed and 30 blocks of dirt everywhere you go.
Water mobs - I was thinking stuff like fish and coral to go with the squid. It'd add some extra incentive to build underwater houses.
Colored glass - Or maybe I should have said 'colorable' glass. Another use for dyes.
Domesticated animals - A pet would be nice, but I'd love to be able to capture and breed pigs, cows, etc. I've heard there are mods of these, but I'd like to avoid these if I could. I'd hate having everything go poof everytime the game gets updated.
And speaking of animals and mods, anyone seem the Mo' Creatures mod?