Guild Wars: Fighting Teleway
Playing against this can be frustrating, as you will frequently nearly kill the telewayers only for them to blink out of existence, cackling. I played a teleway build one evening before Nightfall came out, so I have a reasonable idea of good tactics to use against them. Here's the easiest 2 ways to kill the here-one-moment-gone-the-next telewayers.
1) Spike them hard. Skills that were activating against them before they teleported will still complete and hit them (including attack skills) even if they'd be out of range so if you hit them hard enough they'll die.
2) Look for Shadow of Haste activations. When you re-activate Shadow of Haste, your teleport location is the most recent place you activated it, not the original. If you see one of them putting up the Shadow then snare them near there if possible and pressure them. Save an enchantment removal (Shatter Enchantment, preferably) and then when they teleport and put up Feigned the Shatter will usually kill them.
Watch out for them putting up Shadow inside your base - they'll often try to lure you away from the base then teleport back in and drop an Archer or two before you can get back.