I PERSONALY like Wing for everything it stands from characters to the mecha designs, but it'll be easier to make a list:
1. Great suits. The Wing and all its ideas, (Wing Zero, Wing Zero Custom) has a special place in my heart. Same with the DS, HA, SR, SL, Epyon, and TG.
2. Unique Weapons. Ok, maybe not as unique as the crazy abilities in G Gundam, but each of the 5 Gundams has a unique weapon to go with their name. Beam Scythe/Scissors for Deathscythe, Heat Shotels for Sandrock, Heavyarms is a walking artillery, Dragon Fangs and Flamthrower for Nataku/Shenlong, and who can forget the Buster Rifle/Twin Buster Rifles for Wing/Wing Zero. In SEED, Everyday is free beam rifle/saber day...
3. Unforgetable Characters. Each character seems like they were from different spy movies and ran across a Gundam. The infiltrations and quick wits, FIVE STARS. Great example is how Heero got into the Libra, or when Trowa was playing both sides in EW. Still, can't forget Treize and Zechs. All has their own unique attitude which is why they're all full of awesomeness. Heero is a machine. Trowa is an Acrobat. Duo is a clown. Quattre is a pacifist. Wuffei is a warrior. Zechs is an ace. Treize is a noble. Never have I seen a Gundam show where they have these kind of people in one package. (Except maybe G. XP)
4. Unpredictable Plot. "Quattre? Piloting Zero? Wait, now Wuffei? Duo? Trowa? Zechs?!?! WTF?!?!? I thought Zero was Heero's suit?" I get that a lot from those new to Wing and they already watched Seed, G, and the other series. Take note that in Wing, there is no such thing as "fixed." Switching suits, fighting with allies, all have their reason. Heck, Wuffei with Treize's daughter or Zechs fighting WITH the Gundam pilots? The thrill never ends and will keep you in your toes.
5. Great Opening, Ending, and yes, Even the BGMs. Not sure if you'll agree with me, but the songs from Wing are special. Do also note that most of the titles end with "oin". Last Impression, Rthym Emotion, Just Communication, Love Revolution XP. SEED and its sequel probably tops when it comes to the music, but Wing songs left something in me. Just Communication is the first anime song I've heard. Now, for the BGM. Each BGM in Wing goes well with the scene. One example: Heero transformed to Bird Mode when he saw the OZ shuttle taking off. The BGM is like rushing Heero to catch up with it. Can't fully explain it.
There may be more, but I'm just not thinking of it now...
"I'll kill Zechs. That's my way of saying thanks." -Heero Yuy