So I was going through the FF Rulebook and I couldn't find anything about Arch Enemies. Are they still around? I have had the idea to have Supernova Vet Surfer carrying around Thanos but I wasn't sure if it was legal or not. I've also been wanting to pair up a Sentinal and a few X-men but once again, I'm not sure if it's legal or not.

They've gone the way of the dodo. Feel free to team up Shazam and Black Adam on a JSA team for dual Hypersonic nastiness.

Yeah, the Archenemies rule was taken out of the official rules. The Vendetta feat card was updated to reflect this, too.

Thank you both very much. Now my Sentinals can team up with Destiny for some Prob Control, Joker and Batman and run around together, and Reed Richards can team up with Dr. Doom.

Actually I think the Sentinels got a rule overhaul with the release of the Days of Future Past set in 2006. After that they could be played with X-men/Brotherhood just fine IIRC.
And I don't know if there are any arch enemy pairs worth playing on the same team really. Black Adam and Shazam was the best I could come up with...

Superman and Magog . . .

There probably aren't any really good ones worth playing. During the hiatus I'd cleaned house on alot of my clix and now we're going to start holding local tournaments so I looked at what I had left. I've still got my Sentinels and I figured those might be fun to break out. I used to use the old Calypso LE with them for cheap prob but I've since gotten rid of her. The only cheap prob that I had left was R Domino and R Destiny. That's the main reason that I wanted to know so I could pair the Sentinels up with some X-Men support.

The Sentinels still have rules which award double points for KOing (or being KOed by) figures with the Brotherhood, Morlock, X-Men, and Ultimate X-Men team symbols.

No such rule exists for the Sinestro with regard to the Green Lanterns. The Sinestro rules still state that the figures are arch-enemies. As this term no longer has any meaning in the game, you are allowed to pair Sinestro and GL members up together on a force, but since there was no update, points are still scored normally. There is no doubling anymore for Sinestro.

So I can pair up the Sentinel and Cyclops and if I kill an opposing Cyclops, I would get double points still?

Precisely....

Thank you very much for clearing that up.

My favorite arch-enemy team-up is Black Bolt and Maximus. Both possess the Inhuman keywords, so Black Bolt can BT the other Inhumans while Maximus brings the much needed TK and Outwit to the theme team. Cain Marko and Prof X from Fanatstic Forces is another fun combo, as is Orion and Kalibak.

Kalibak is destroying cars!!!

Only IF the Sentinel did the killing blow, no? Cyclops on an opposing Cyclops wouldn't score the double points.

Since there is no arch enemy machanic anymore, would the BFC alpha strike be defunct now as it allows you to choose characters with a team symbol as your arch enemy?