Slayers
Dragon Slave it. For particularly large versions Giga Slave is more appropriate. Or for Zel/Amelia fans, a Ra Tilt will probably work since we all know that those adds are pure evilness anyway. ^_^
Tell Valgarv that the popup insulted his Garv-sama.
If it asks a question, giggle evilly and say "Sore wa Himitsu desu!" and watch it die from frustration.
Materialize a tail with a pink bow, draw your mace and Bash away while yelling "NAMAGOMI MAZOKU!"
Say you are the great Hero Valuun and will slay the foul beast with a single might slash, all for your dear Miss LaLa.
"Whatever...Fireball!"
cry out "Popup-sama" in your best sappy Syphiel voice and glomp the sucker.
Grab your lightSaber and yell Light Come Forth! (or Hikari o for you sub fans) and watch the ad cower and flee.
Put on a weird floppy hat and challenge the ad to a duel, then follow it all over the world until you can prove which is the better man.
If you should happen to mistake it for the ever appearing Vrumagen, break the little red crystals on it's forehead.
Summon a bunch of jellyfish. that always works.
Throw a rock at it.
Zel: I resent that.
SlayersML
sic the 50 chibikopixels on it
stick it in a room with the Naga/Kodachi/Jinnai clones
GundamWing
Point at the screen and say "Omae o Kurosu" in your best Heero voice.
Braid your hair, pull out a beam scythe and Say "I'll see you in Hell!" while laughing manically and slashing for all you're worth.
Pull half your hair over your face, say nothing and blow it to kingdon-sank with more artillery than 3 full battle ships.
Tell the Popup to surrender and when it doesn't pinch it to death with the sandrock.
Dress up as Quatre and Tell your Maganac Warriors to kill it and they'll only be to happy to oblige, and you'll get called Quatre-sama and get compliments on your violin playing, no matter how bad as a bonus.
Adjust your painfully tight ponytail, then draw your chinese sword, pose, make a long run on sentence justice speech and watch the popup crumble into little bits of dust. (N/A to Amelia)
Yell: "HEEE~~~EEEE~~~~EEEEE~~~~ROOOO~~~OOOO!" and watch it flee back to the colonies.
Fushigi Yuugi
Tell Miaka that it tastes good (or Lina, Gourry, Naga, Ranma, C-ko, etc, etc...)
Dress it as HotoHori and give it to Nuriko.
"no Da" it to death.
Sailor Moon
Evil Popup Magical Mouse OBLITERATION!
Utena
If it has a flower, play the apocolypse song, draw your trusty sword of Dios and Duel it out!
Pokemon
Shout "PI-KA-CHU!" and thundershock the Popup
Ranma1/2
Give it to Azusa: she'll give it a kawaii french name and keep it in her room "forever and ever and ever"
Throw it into the Spring of Drowned useful Information and watch it die from paradox.
If it depresses you, ShishiHoukoudan it into a spot of purple goo.
If it Obviously feminine, Waves your bonbori threateningly and say "Girltype popup, you I kill!"
If it is a guy's add, Glomp it in a skimpy chinese dress and say "Wo da ai ren, boy type ranma, you I love!"
Blast the ad with exploding okonomiyaki or punt it into the stratosphere with your spatula
Tell it that it owes you 50,000 yen or a two hour long photo shoot, payment due, now.
take a picture and threaten blackmail
Call it "Pigtail popup Goddess!" and glomp it
put on a green leotard, pull your hair into a ponytail on the side of your head, put a black rose between your teeth, wave a long gymnastics ribbon threateningly while reciting "If I weren't a lady! ...aren't you all lucky I was raised better than that!" then laugh manically as you leap from rooftop to rooftop as your dramatic exit scene of black rose petals.
Splash it with cold water
Splash it with hot water
grow fangs, quick-draw your 20 pound parasol and charge, yelling, "Popup Ad, prepare to die!"
If all else fails, pull out your Frilly Pink Hammer of justice (Harukami only, the rest of you will have to use hnormal hammerspace mallets) and pound it into a vauguly rectangular splat while yelling "POPUP NO BAKA!"