No, what's really whee is the MPS power gauntlet, after they added the railgun, but before the heat mechanic. Has a ton of recoil, but no cost to fire it save a tiny amount of power. Just aim it slightly below the horizon and spam the mouse button. You get shot backward stupidly fast.
Nowadays, however, it just sets you on fire.
Close second: MPS suit with jetpack, jetboots, flight control, and maybe the sprint/walking speed assist (not sure if it makes any difference). Sprint, jump, then turn on flight control. Again, it's pretty ridiculous. I timed it; I went 1000 blocks in about 17 seconds.
Third place comes from Clockwork Phase. Put nine temporal gears into a clockwork (or something with even better speed if there is such a material), and put that into a Chronomancer's Hourglass of Wind. I tried this on a server and managed to fly into chunks that hadn't even been sent to my client yet.
A word of warning: I found the Wind hourglass to be really hard to turn off after I'd gone any appreciable distance with it when I was on a server. Singleplayer's fine, however.