Ninjak and Bloodshot. Don't know if this has happened but it should again anyway.
I'd imagine Bloodshot and Agent Venom would be an interesting combo. They have a somewhat similar powerset and history.
XO Manowar and Thor because of their similar personalities.
Deadpool and Punisher. I'd love to see some scenario where Punisher is lumped with Deadpool for a long time period, and they're forced to work together. He'd be bursting blood vessels like it's his job.