Eneloop cells are the best for cost effectiveness and capabilities. (They're a kind of low self discharge NiMH cells.) Most cumulative lifetime capacity potential, but not the highest capacity per charge. For higher capacity per charge but unfortunately lower (but still relatively high compared with other cells) total lifetime capacity potential there are the "XX" Eneloop cells.
The newest version of the regular Eneloops get up to 1800 cycles down to 80% usable capacity per charge, and have a very low self discharge rate, holding up to 70% of a charge after 5 years, if they're just sitting on a shelf, or similar, if I remember these numbers correctly. This means more of their charge can get used rather than wasted from self discharging over time. This also means that they can be stored charged and ready to use.
What I do is have extra sets of cells charged and ready to use so that when the cells I'm using in a device get low, I'll take them and put them on the charger, and use the charged ones that are waiting. No waiting for the cells to charge. As convenient as primary cells (actually more convenient, since you don't have to keep buying more of them), and a lot more cost effective in the long run. (1 Eneloop AA cell approximately equals 1000 or more name brand alkaline AA cells in total cumulative lifetime capacity potential.)
Not sure if these 1800 cycle ones are common in the US yet (they're made in Japan). It might still be the 1500 cycle ones over here that are more common. Either way, they're still great batteries.
They make both AAs and AAAs.
A great charger is the MH-C9000. And of course, to get the most out of your rechargeable cells, you should learn how to properly take care of them and how to optimally use your specific charger for them. Rechargeable batteries are kind of like an investment. Candle Power Forums is a great place to look for more info. Maybe do a Google search for Candle Power Forums Eneloop MH-C9000
or similar for more into.
Also, I believe that the Duracell pre charged/stay charged NiMH cells with the white insulation on the top of the cells around the positive contact are rebranded Eneloops. They're often referred to on-line as "Duraloops." I haven't tried them personally though. I just order my Eneloops on-line from either Amazon or Thomas Distributing. Might be a good idea to stay away from ebay though, since there are reports of some counterfeits out there.
Can i pick a lithium one? Or will it not work ?
"Lithium" AA and AAA primaries? Yes, most likely. "Lithium" rechargeables (such as LiFePO4 or Li-ion)? No, they're the wrong voltage.
As mentioned, NiMH cells are your best bet.
If you have any more specific questions, including how to care for your rechargeable cells, I can likely answer them here for you as well.