Safari Zone: caught a Phanpy, Heracross and a Girafirag, which I believe ends my list of Safari Zone exclusives. I forget if you can catch a Donphan in there, so I just plan on evolving up the Phanpy.
Finally did some trading with Rhon's Pokemon Ruby: Alakazam, Machamp, Golem and Huntail. One nice thing about trade evolutions is that the receiver gets pokedex credit for both monsters. So by giving Rhonda a Kadabra that immediately evolved into Alakazam she got a +2 to her 'dex. Then trading it right back to me rounded out my list. The Huntail evolves from trading a Clamperl equipped with the Deepseatooth. The Deepseatooth is one of the Ruby/Sapphire "choice" items. You get to choose either the Deepseatooth or the Deepseascale and the other disappears forever (like the Root/Claw Fossils.) Note to self: choose the scale in Ruby. Also scored a Mawile and a Seedot, two monsters found only in Ruby.
Wasted a lot of time fishing on Route 119 for a Feebas. The damn things show up in a randomized 1-6 squares out of a possible 4 million squares, so they're grotesquely hard to locate. In a weird don't-kill-the-prehistoric-butterfly moment, the squares are reset every time the popular phrase in Dewford Town changes. I have a sneaking suspicion that Feebas (and, by extension, Milotic) will be among the very last pokemon I catch.
Difficult catches: Nosepass, Crobat and Snorunt. The Nosepass can only be found in Granite Cave, hiding inside the smashable rocks. Of course he's randomly uncovered, so it takes lots of Rock Smashing to find him. I've been through Granite Cave several times before and I finally hit a lucky Smash. Nosepass is, of course, horrendously ugly.
Crobat - as I discovered about 100 hours ago - only appears if your Golbat likes you. Getting a pokemon to like you is easy but time consuming. Basically you just have to carry him around forever and try to minimize him dying in battles. I tucked the Golbat into my belt for hours, with him just shy of his next level-up. Periodically I'd take him to the lady in Verdanturf City who can tell you if your pokemon like you. Her assertions are merely categorical; it took several more hours of Golbat-sitting to get him to evolve even after she claimed he "liked [me] very much."
The toughest part about catching a Snorunt was finding time to play when the tide is out. Snorunts are only found at the bottom of Shoal Cave during low tide, which always seems to be when I'm not playing. So early one morning (around 8am) I picked up Sapphire and saved my game once I was deep in Shoal Cave's ice room. Then I continued later at my convenience. Lucky that the tide can't come in while you're innocently sitting in the flood zone.
What do you do when your Shelgon needs some quick experience? I entered him as part of my team against the Elite Four. Putting him in the catbird seat for my second run at the Championship moved him up several levels without much effort.